Process for producing l-cysteic acid and use thereof

Abstract

The invention relates to a process for producing L-cysteic acid, comprising the reaction of O-phospho-L-serine (OPS) with a salt of sulfurous acid (sulfite) and a cysteate synthase (CS-enzyme) of enzyme class EC 2.5.1.76 in a biotransformation process. The L-cysteic acid according to the invention can be decarboxylated to form taurine. The invention also relates to the use of the L-cysteic acid produced for the production of taurine.

Description

[0001] Process for the production of L-cysteic acid and its use The invention relates to a process for the production of L-cysteic acid comprising the reaction of O-phospho-L-serine (OPS) with a salt of sulfurous acid (sulfite) and a cysteate synthase (CS enzyme) belonging to the enzyme class EC 2.5.1.76 in a biotransformation. The L-cysteic acid produced according to the invention can be decarboxylated to taurine. The invention further relates to the use of the produced L-cysteic acid for the production of taurine. L-cysteic acid ((R)-2-amino-3-sulfopropionic acid, 3-sulfo-L-alanine, CAS 498-40-8) is a non-proteinogenic L-amino acid that can be detected in nature as an oxidation product of the proteinogenic amino acid L-cysteine, e.g. in sheep's wool. Cysteic acid is also an intermediate in coenzyme M biosynthesis (CoM, 2-mercaptoethanesulfonic acid, CAS 3375-50-6) of methanogenic archaebacteria.The biosynthesis pathway of L-cysteic acid in methanogenic bacteria starts from O-phospho-L-serine (OPS, L-serine-O-phosphate, L-2-amino-3-hydroxypropionic acid-3-phosphate, CAS 407-41-0), which reacts with sulfite to form L-cysteic acid in a reaction catalyzed by a cysteate synthase (CS enzyme), according to equation (1): (1) OPS + SO3. 2--> L-cysteic acid + HPO42- Graham et al., Biochem. J. (2009) 424: 467-478 describe that for a gene from Methanoscarcina acetivorans related to threonine synthases, which is produced recombinantly in E. coli and accumulated as an enzymatically inactive protein in so-called inclusion bodies (protein aggregates as inclusion bodies), detectable enzyme activity is only measurable after complex renaturation of the inclusion bodies. After renaturation, it was demonstrated that in analytical tests (HPLC and mass spectroscopy) with the renatured protein, L-cysteic acid is formed from the reaction of commercially available (chemically synthesized) OPS and sulfite according to equation (1). These studies assigned the activity of a cysteate synthase to the renatured protein from M. acetivorans and established its genetic relationship to threonine synthases. L-cysteine ​​acid can be produced chemically, e.g.by oxidation of cysteine ​​with chlorine in alcoholic solution, with bromine in HCl or iodine-HCl in DMSO or by oxidative cleavage of cystine. Furthermore, L-cysteine ​​acid can also be produced by oxidation of L-cysteine ​​sulfinic acid. The known processes for the chemical production of L-cysteine ​​acid, which are not considered sustainable, use environmentally hazardous chemicals and are not well accepted by consumers, particularly in the food, cosmetics and pharmaceutical sectors. L-cysteine ​​acid can be used, for example, in fish farming or in the cosmetics sector, e.g. as an ingredient in Regu®-Slim (DSM) for skin care. In peptide chemistry, L-cysteine ​​acid is used as a water-soluble protecting group. L-cysteine ​​acid can also be converted to taurine by decarboxylation. Graham et al. (2009, see above) have shown that in E.coli, the CS enzyme with a molecular weight of 44 kDa is not produced in active form during heterologous expression, but is only enriched in inactive form in inclusion bodies. The solubilization of the inclusion bodies and refolding to the active enzyme led to a very low yield of 3 mg of refolded protein per L of E. coli culture and was therefore not suitable for a preparative biotransformation process for the production of L-cysteic acid on an industrial scale. Without refolding, enzyme activity was only detectable in Graham et al. (2009, see above) when the CS enzyme was expressed as a 103 kDa CS fusion protein, with both the enzyme yield and the specific enzyme activity of 0.015 U / mg protein being very low. This state of the art shows that active CS enzyme can only be produced in E. coli with great effort, in a costly process and with low yields. Joo et al. (2018), J. Agric. Food Chem.66: 13454 – 13463, describe a metabolic engineering approach using a genetically modified strain of the bacterium Corynebacterium glutamicum optimized for sulfur utilization to produce taurine. The CS activity of the gene expressed in C. glutamicum was analytically demonstrated using enzyme assays. The activity of the CS enzyme in taurine-producing strains was indirectly determined. As shown in Fig. S2 of the Supporting Information to Joo et al. (2018, see above), CS-expressing C. glutamicum cells accumulate OPS, the substrate of the CS reaction, as well as serine, cysteine, and taurine, predominantly intracellularly. No information was provided on the production of L-cysteic acid. Joo et al. (2018, see above)) shows that the simultaneous presence of OPS and CS enzyme in a cell is not sufficient for the effective production of L-cysteic acid, even if the intracellular production of other sulfur-containing compounds such as cysteine ​​and taurine occurs with measurable yields in the same strain. Tevatia et al., Algal Research (2015) 9: 21-26, describe the natural production of taurine in microalgae, with L-cysteic acid also being detected as an intermediate. As described in Fig. 1 of Tevatia et al. (2015, see above), a biosynthetic pathway in algae leads from L-serine to L-cysteic acid ("cysteate" in Fig. 1). However, the pathway does not include the enzymatic reaction of a CS enzyme according to equation (1). None of the described biosynthetic pathways leads to L-cysteic acid via OPS.The intracellular L-cysteic acid content was very low and accompanied by several byproducts such as methionine, cysteine, cysteine ​​sulfinic acid, hypotaurine, and taurine that made purification difficult, making the cultivation of microalgae unsuitable for the production of L-cysteic acid. US 2019 / 0062757A1 (KnipBio) describes a metabolic engineering approach using heterologous production strains for the production of taurine or its precursors. Strains were described that express the CS enzyme and other biosynthetic genes from taurine metabolism in various configurations. The yields achieved for hypotaurine and taurine were very low at a maximum of 419 ng / ml. Yields for the production of L-cysteic acid were not stated. In this prior art, CS gene constructs were used, but no enzyme assay was performed to detect CS enzyme activity.Furthermore, it has not been demonstrated that L-cysteic acid can be produced biotechnologically in preparative quantities using this metabolic engineering approach. Likewise, it has not been disclosed whether the strains described in the document are suitable for producing OPS or CS enzyme for use in a biotransformation to produce L-cysteic acid according to equation (1). Steinfeld et al., ACS Chem. Biol. (2014) 9: 1104-1112 describe the enhanced intracellular production of OPS in an E. coli strain with a deleted serB gene. Enhanced extracellular production of OPS has not been described (see Fig. 5 in Steinfeld et al.). EP 2444 481 B1 of CJ CheilJedang Corporation (KR) describes a process for the production of L-cysteine, whereby a strain with reduced SerB activity is used to produce OPS, which is then converted to L-cysteine ​​in an enzymatically catalyzed reaction with sulfide or thiosulfate.The enzyme class used in this process, O-phosphoserine sulfhydrylases (OPSS, EC 2.5.1.65), is not known to be able to utilize sulfite as a substrate in the sense of a CS enzyme. In fact, Steiner et al. are investigating this in J. Bacteriol. (2014), 196: 3410-3420 investigated the reaction mechanism of the OPSS enzyme from Mycobacterium tuberculosis and found that, in contrast to Na2S (sulfide) and Na2S2O3 (thiosulfate), salts of sulfurous acid, such as Na2S2O5 and Na2SO3, are not suitable as S donors for the reaction with an enzyme-bound aminoacrylate intermediate, where the aminoacrylate intermediate originated from the binding of OPS to the OPSS enzyme with phosphate cleavage (see Fig. 2 in Steiner et al., 2014, supra). EP 2444 481 B1 thus discloses the inactivation of the serB gene, also known from Steinfeld et al. (2014, supra), for the production of strains that then produce OPS.The OPS could then be used in a biotransformation with OPSS enzymes to produce cysteine. The state of the art includes the biotechnological production of OPS. However, the state of the art does not offer a production process for the CS enzyme that would be suitable for providing CS enzyme with sufficient activity for a previously unknown industrially applicable process of biotransformation of OPS with a sulfite, in which L-cysteic acid is produced on a preparative scale for further use. Therefore, there is a need for an environmentally friendly and sustainable process for the production of L-cysteic acid on a preparative scale, for which a biotechnological process is suitable.Given the trend away from chemically produced ingredients driven by consumer demand, the aim of the invention was to provide a biotechnological process for producing L-cysteic acid by biotransformation, suitable for use on an industrial scale. The aim of the present invention was to provide an industrially applicable process for the cost-effective production of L-cysteic acid by biotransformation of OPS, instead of a chemical process and by bypassing an L-cysteic acid production strain produced by metabolic engineering, and to use the L-cysteic acid produced in this way for further use, e.g. for the production of taurine. This object is achieved by a process for producing L-cysteic acid, comprising the reaction of O-phospho-L-serine (OPS) with a salt of sulfurous acid (sulfite) and a cysteate synthase (CS enzyme) belonging to the enzyme class EC 2.5.1.76 in a biotransformation.In the context of the present invention, a distinction is made between manufacturing processes as follows: 1. Chemical processes 2. Biotechnological processes: a) by metabolic engineering Metabolic engineering (also called “pathway design”), in contrast to biotransformation, is a biotechnology method in which the metabolic pathways of an organism are modified by optimising or altering genetic and regulatory processes. By supplementing the genome with enzyme genes, new or modified enzymes can be introduced into an organism or genes of endogenous enzymes can be expressed at a higher or lower level, thereby establishing new metabolic pathways in an organism or strengthening or weakening existing metabolic pathways. The aim of metabolic engineering is for the organism to produce either a new metabolic product or a cell-derived metabolic product with an increased yield.In a metabolic engineering process, no starting materials specific for the metabolite, such as an enzyme substrate such as OPS in the present invention, are used, but merely a nutrient medium which is required for the growth of the organism in question and is composed of a C source (e.g. glucose), an N source (e.g. an ammonium salt or a complex amino acid mixture such as peptone or yeast extract) and other salts required for growth. Such nutrient media are known to the person skilled in the art from microbiological practice. b) by biotransformation Biotransformation is defined as the conversion of one or more reactants into a product under enzymatic catalysis, wherein the enzyme substrate is added to a reaction mixture with the enzyme.In the reaction mixture, the added enzyme substrate, such as OPS in the present invention, is enzymatically converted, in the present invention by an enzyme selected from the class of cysteate synthases (CS enzyme, EC 2.5.1.76) in the presence of a salt of sulfurous acid. The reactant(s) can originate from chemical or biotechnological production. The OPS used in the process according to the invention can originate, for example, from chemical synthesis or from biotechnological production by culturing a production strain. The enzyme used for the enzymatic catalysis preferably originates from biotechnological production by fermentation of a production strain from the Enterobacteriaceae family that heterologously expresses the CS enzyme. An advantage of the present invention is that the process according to the invention for producing L-cysteic acid from OPS and sulfite using the CS enzyme is a biotransformation process.This means that this is a highly targeted, specific reaction and, for example, does not require complex culture steps or purification steps from a microorganism culture. Furthermore, high space-time yields can be easily achieved with biotransformation by optimizing the reaction conditions and the amount of reactants and enzyme used, something that is much more difficult to achieve through strain optimization in metabolic engineering. Overall, the process according to the invention is economically simple to implement and controllable. The reaction (1) according to the invention is catalyzed by the enzyme cysteate synthase (CS enzyme), which belongs to the enzyme class EC 2.5.1.76. A CS enzyme in enzymatically active form is a protein capable of catalyzing the synthesis of L-cysteic acid from OPS and a salt of sulfurous acid, as described in the following CS enzyme activity test.The CS enzyme activity test can be carried out as follows: i) A CS enzyme produced by cultivation in a shake flask or in a fermentation can be used in the reaction as follows: - as an aliquot from the culture broth which has not been further processed, or - as an aliquot of the cell suspension after re-isolation of the cells from the culture broth, e.g. by centrifugation, or - in the form of an aliquot of the cell homogenate a) after mechanical disruption of the cell suspension, or b) in the form of chemically permeabilized cells (e.g. by chloroform), or - as a cell extract after separation of particulate components from the cell homogenate, or - as an enzyme which has been purified, for example by chromatography. The total protein concentration obtained in each case can be determined, for example, as described in Example 3 of the present invention, using a Qubit 3.0 fluorometer from Thermo Fisher Scientific using the “Qubit. ®Protein Assay Kits" according to the manufacturer's instructions. ii) OPS (10 mM final concentration) and Na sulfite (20 mM final concentration) are placed in a solution buffered to pH 7 with potassium phosphate, and the reaction is started by adding the CS enzyme. The assay volume is 10 ml. The temperature at which the assay is carried out is 30°C. The amount of CS enzyme used depends on the degree of purification. If culture broth, cell suspension of the reisolated cells, or cell homogenate is used, at least 0.1 mg of the enzyme fractions prepared in i) is used. In the case of purified CS enzyme, at least 10 µg of the purified enzyme fraction is used.1 h, 2 h, and 4 h after the start of the reaction, 1 ml of the test mixture is taken, centrifuged for 10 min, and the content of OPS and L-cysteic acid is determined by calibrated HPLC (see Example 4). The reference substances used for calibration are commercially available (Sigma-Aldrich). The method according to the invention is preferably characterized in that the CS enzyme is produced by culturing a microorganism strain of the Enterobacteriaceae family. It is preferred that the cds encoding the CS enzyme be expressed heterologously in the microorganism strain of the Enterobacteriaceae family, and particularly preferably in enzymatically active form. Heterologous expression is understood to mean the expression of the cds of a gene or the cds of a part of a gene in a host organism that does not naturally possess this gene or gene fragment.The introduction of the CDs of the heterologous gene into the host organism involves the use of recombinant DNA technology. The CDs of the heterologous gene can be introduced into the host organism by integration into its genome or extrachromosomally in the form of an autonomously replicating gene construct (plasmid, vector). The preferred method is to introduce the CDs of the heterologous gene into the host organism in the form of an autonomously replicating gene construct (plasmid, vector). Depending on the genetic element (promoter) that controls the expression of the CDs of the heterologous gene, a distinction is made between constitutive expression and induced expression. In constitutive expression, gene expression is active (unregulated) during all phases of cell cultivation. In induced expression (regulated), gene expression is stimulated by adding an inducer molecule to the cell culture, such asof the inducer molecule IPTG for inducing the tac promoter in Examples 3 and 7 of the present invention. Induced expression is preferred, in which gene expression is stimulated by adding an inducer molecule to the cell culture. Homologous expression, on the other hand, refers to the overexpression of the cds of a gene in a host organism from whose genome this gene originally originates. A heterologously expressed protein, e.g., an enzyme, can be present in an enzymatically active form or accumulate in an enzymatically inactive form, e.g., in inclusion bodies.Heterologous expression of the CS enzyme in enzymatically active form accordingly means that i) the cds of the gene coding for the CS enzyme, which is introduced into the host strain, is not encoded in the genome of the host strain, ii) at least the cds of the gene coding for the CS enzyme is chromosomally integrated into the genome of the host organism by recombinant DNA technology or, preferably, is introduced extrachromosomally into the host organism by an autonomously replicating vector, and iii) that a CS enzyme is expressed from this cds in enzymatically active form. The heterologously expressed CS enzyme is particularly preferably expressed by the microorganism strain in enzymatically active form. This means that a CS enzyme is expressed from the heterologously introduced cds which, after protein biosynthesis and optionally post-translational modification, such asthe incorporation of a cofactor such as pyridoxal phosphate in the case of the CS enzyme (see entry in the KEGG enzyme database under entry number EC2.5.1.76) in the microorganism in enzymatically active form. Expressed in enzymatically active form excludes the possibility that the protein is first produced as an inactive protein in inclusion bodies and only exists in enzymatically active form after renaturation. In summary, in a particularly preferred embodiment, the process is characterized in that the CS enzyme is produced by cultivating a microorganism strain of the Enterobacteriaceae family which expresses the CS enzyme heterologously and in enzymatically active form. In the context of the present invention, a reaction mixture is defined as a mixture of reactant (starting material), enzyme and optionally further reactants, in which the reactant is converted into a product.The yield of the reaction within the meaning of the invention is defined as the amount of reactant used which is converted to the product under the reaction conditions. The yield can be given as the absolute yield of the product (mmol or g), as the volume yield in absolute, volume-related amount of product (mM or g / L) or as the relative yield of product as a percentage of the reactant used (taking into account the molecular weights of the reactant and the product), also referred to as the percentage yield. For the purposes of this invention, the term cultivation or synonymously culture of microorganism cells includes both culture processes in shake flasks and fermentation processes. The medium used for the cultivation or culture of the microorganisms is referred to as the cultivation or culture medium or, in the case of fermentation, also the fermentation medium. By cultivating / culturing / fermenting the production strain in the cultivation, culture orThe culture broth / fermenter broth is created from the fermentation medium. The culture broth / fermenter broth consists of the biomass of the cells of the production strain and the culture supernatant / fermentation supernatant, which has been freed of biomass and formed during the cultivation process from the culture medium and the metabolites secreted by the cells. Fermentation is a process step for the production (cultivation) of cell cultures on an industrial scale (production scale). In this process, a preferably microbial production strain is induced to grow under defined conditions of culture medium, temperature, pH, oxygen supply, and medium mixing. The goal of fermentation is, depending on the configuration (genetic makeup) of the production strain, the production of a protein / enzyme or a metabolite, in each case with the highest possible yield for further use.The components of the process according to the invention, OPS and CS enzyme, can be produced by fermentation. The end product of the fermentation is a fermenter broth consisting of the biomass of the cells of the production strain (fermenter cells) and the fermentation supernatant, freed from the biomass and formed during the fermentation from the culture medium and the metabolites secreted by the fermenter cells. The target products of the fermentation can be found in the fermenter cells or in the fermentation supernatant. Thus, OPS is found in the fermentation supernatant, while the CS enzyme is found in the fermenter cells. Shake flask culture is used for the cultivation of microorganisms on a laboratory scale, in contrast to production scale fermentation.Although shake flask culture also requires a specific medium and pH, and cultures are carried out in the presence of oxygen and under constant agitation (shaking), more defined conditions regarding the medium, temperature, pH, oxygen supply, and medium mixing can be adjusted and regulated in the fermenter. Culture on a smaller scale, e.g., in a shake flask, can also be used as a pre-culture for inoculating a larger-scale culture, e.g., a fermenter. A production strain is defined as a microorganism strain suitable for producing a product, e.g., by fermentation. The production strain is characterized by its ability to (improve) the production of the product through genetic modification.The genetic modification can consist of a change in the genome (chromosomal alteration), by the introduction of an autonomously replicating extrachromosomal genetic element such as a plasmid, or by a combination of chromosomal and extrachromosomal alterations. An example of a production strain with a chromosomal alteration is the E. coli W3110-^serB strain described in Example 1 for the production of OPS. An example of a production strain produced by the introduction of a plasmid is the E. coli JM105 x pCSma-pKKj strain described in Example 3 for the production of the CS enzyme. The microorganism strain carrying the extrachromosomal genetic element is referred to as the host strain or host organism, and the extrachromosomal genetic element is referred to as the gene construct, plasmid, vector, or expression vector. The open reading frame (ORF, synonymous with cds, coding sequence) is the region of the DNA orRNA is a sequence of genes that begins with a start codon and ends with a stop codon and codes for the amino acid sequence of a protein. The ORF is also called the coding region or structural gene. A gene is the section of DNA that contains all the basic information for producing biologically active RNA. A gene contains the section of DNA from which a single-stranded RNA copy is produced by transcription and the expression signals that are involved in regulating this copying process. Expression signals include, for example, at least one promoter, a transcription start site, a translation start site, and a ribosome binding site (RBS). Other possible expression signals include a terminator and one or more operators. mRNA, also called messenger RNA, is a single-stranded ribonucleic acid (RNA) that carries the genetic information for building a protein.mRNA provides the blueprint for a specific protein in a cell. The mRNA molecule carries the message from the genetic information (DNA) necessary for protein construction to the protein-building ribosomes. In a cell, it is formed as a transcript of a section of DNA belonging to a gene. The genetic information stored in the DNA is not altered. Genes of eukaryotic organisms are predominantly so-called mosaic genes and, unlike prokaryotic genes, also contain non-coding sections called introns (intragenic regions). Coding sequences, so-called exons (expressed regions), are DNA segments of a eukaryotic gene that, after transcription into RNA, are translated by the ribosomes into the amino acid sequence of a protein. The introns are spliced ​​from the primary transcript after transcription of DNA into RNA.The protein-coding RNA freed of introns is called messenger RNA (mRNA), also known as "mature" mRNA. This undergoes further modifications such as capping and polyadenylation. The coding region of the mature mRNA is then translated into the protein sequence. If a eukaryotic gene with an exon / intron structure is to be expressed in prokaryotic organisms, it is necessary to retranslate the protein sequence or the coding region of the mature mRNA into intron-free DNA, since the processing of the exon / intron structure does not occur in prokaryotes. When reference is made in the context of this invention to gene sequences derived from the protein sequence or from mRNA, precisely this process of backtranslation is meant. It is preferred that the backtranslation of the protein sequence or the mRNA sequence into DNA sequence be accompanied by sequence optimization, i.e., adaptation to the codon usage of the corresponding prokaryote (codon optimization).A gene construct is a DNA molecule in which a gene is linked to other genetic elements (e.g., promoter, terminator, selection marker, origin of replication). A gene construct within the scope of the invention is a circular DNA molecule and is referred to as a plasmid, vector, or expression vector. The genetic elements of the gene construct bring about its extrachromosomal inheritance during cell growth and the production of the protein encoded by the gene. The abbreviation WT (Wt) stands for wild type. A wild-type gene is the form of the gene that has arisen naturally through evolution and is present in the wild-type genome. The DNA sequence of wt genes is publicly accessible in databases such as NCBI (National Center for Biotechnology Information). A microorganism strain with a wt genome is referred to as a wt strain.L-cysteic acid from the inventive biotransformation of OPS with a salt of sulfurous acid can either be used directly without further processing steps or enriched or purified using known methods. Such methods are known to the person skilled in the art from processes for isolating amino acids. They include, for example, filtration, centrifugation, extraction, adsorption, ion exchange chromatography, precipitation, and crystallization. The process is preferably characterized in that the reaction mixture containing the L-cysteic acid is used without further processing, purification, or isolation steps. In an alternatively preferred embodiment, the process is characterized in that the L-cysteic acid produced is isolated from the reaction mixture.In the context of this invention, denaturation refers to a structural change in biomolecules such as proteins, which is associated with a loss of the biological function of the molecules, although their primary structure remains unchanged. A denatured protein is characterized by being enzymatically inactive, i.e. for CS enzymes within the meaning of the present invention, that they are not able to catalyze the synthesis of L-cysteic acid from OPS and a salt of sulfurous acid. Denaturation can be due to physical or chemical influences. Incorrectly or incompletely folded, enzymatically inactive proteins can accumulate in the cell in protein aggregates (so-called inclusion bodies) and can be regarded as naturally denatured proteins.Inclusion bodies are observed primarily at high expression levels, when the resulting high concentration of newly synthesized protein chains favors aggregation over folding into the enzymatically active three-dimensional form. Whether a heterologously expressed protein will be obtained in the form of insoluble inclusion bodies or in an active form cannot be predicted and depends not only on the primary structure of the protein chain (sequence of the amino acid sequence), but also on the expression system used and parameters that can control the rate of protein biosynthesis (e.g., cultivation temperature, induction strength for inducible promoters). In the case of the present invention, however, it was surprising that the cysteate synthase from Methanoscarcina acetivorans could be produced in enzymatically active form in E. coli, since the same protein was previously produced in E. coli when heterologously expressed (Graham et al., 2009, see above).coli was only produced in an inactive form in inclusion bodies. Renaturation refers to the reconversion of denatured proteins into their biologically active spatial structure. In renaturation in protein biochemistry, chaotropic compounds are used to bring denatured protein back into solution in inclusion bodies before protein renaturation is enabled by removal of the chaotropic compound. In protein chemistry, urea and guanidine hydrochloride are mainly used for this purpose. The process is preferably characterized in that the CS enzyme is used in the reaction without a prior renaturation step. The renaturation steps include the following process steps: dissolving the denatured protein in a medium containing a chaotropic compound and subsequent removal of the chaotropic compound. The extent to which the chaotropic compound needs to be removed depends on the respective protein.The chaotropic compound can be removed, for example, by dialysis, selective binding of the chaotropic compound to a support material, selective binding of the protein to be renatured to a support material and subsequent elution under renaturing conditions, or by diluting the chaotropic compound below a critical concentration below which it no longer has a denaturing effect (see, for example, Graham et al., 2009, see above). Methods of protein renaturation are described in the state of the art. Renaturing conditions include, for example, dissolving the denatured protein in a 6 M aqueous urea solution or 6 M aqueous guanidine HCl solution. Dilution or removal of the chaotropic compound below a critical concentration depends on the respective protein and means that the concentration of the chaotropic compound, such asUrea or guanidine is reduced below a concentration at which the protein in question can once again assume the three-dimensional structure of its active form. Chaotropic compounds are chemical substances that disrupt ordered hydrogen bonds in water. Chaotropic compounds include barium salts such as barium chloride or barium acetate, guanidine hydrochloride, thiocyanates such as guanidinium thiocyanate, perchlorates, iodides, butanol, phenol, thiourea, urea and / or surfactants. Surfactants (also known as detergents or soaps) are organic compounds that act as surface-active substances, i.e. thanks to their structure they arrange themselves at the interface between two phases in such a way that they lower the interfacial tension (= surface tension) and thus enable wetting, for example. By reducing the surface tension they promote the mixing of two phases, under certain circumstances to the point of forming an emulsion.Surfactants are characterized by a polarity of the molecular structure, whereby one part of the molecule has hydrophilic properties, which mediate solubility in water, and the other part of the molecule has hydrophobic properties, whereby surfactants solubilize hydrophobic compounds and contribute to solubility in water. The surfactants used are non-ionic surfactants (polyalkylene glycol ethers, fatty alcohol propoxylates, alkyl glucosides, alkyl polyglucosides, octylphenol ethoxylates such as Triton X-100, nonylphenol ethoxylates), anionic surfactants (alkyl carboxylates, alkylbenzenesulfonates, alkylsulfonates, fatty alcohol sulfates such as sodium lauryl sulfate, alkyl ether sulfates, sulfoacetates), cationic surfactants based on quaternary ammonium compounds (distearyldimethylammonium chloride, “esterquat”) and / or zwitterionic (amphoteric) surfactants based on betaine (e.g. “cocoamidopropyl betaine”) or sulfobetaine (e.g. cocoamidopropyl hydroxysultaine).In a preferred embodiment, the process is characterized in that the CS enzyme is used in the reaction without a prior renaturation step. Working without a renaturation step has a major economic advantage, because the complex, costly and environmentally damaging renaturation steps described above are not required. In the case of production of the CS enzyme by culturing a production strain, particularly when the CS enzyme is produced by fermentation, the host cells expressing the CS enzyme do not first have to be mechanically or chemically disrupted in a complex and costly process that pollutes the environment, e.g. through waste, and inclusion bodies, in which the enzyme accumulates in an inactive form, for example in Graham et al. (2009), have to be isolated from the cell lysate and renatured in order to be able to use the protein for enzymatic reactions.A prerequisite for the process according to the invention for producing L-cysteic acid by biotransformation is the availability of OPS. OPS can be produced chemically or biotechnologically, e.g. by fermentation of an OPS production strain. Possible methods for the chemical production of OPS include phosphorylation of L-serine or the production of the racemate O-phospho-D / L-serine, which can be used directly, or OPS is previously obtained from the racemate, e.g. by racemate resolution. The process for producing L-cysteic acid is preferably characterized in that the OPS used in the reaction is produced biotechnologically. This is carried out by cultivating an OPS production strain. Particular preference is given to the biotechnological production of OPS by cultivating an OPS production strain in which OPS accumulates in the cell culture supernatant (extracellularly).The person skilled in the art can use isotope analysis to determine whether a substance such as OPS, which he intends to use as a starting material in the process, originates from chemical or biotechnological, e.g., fermentative production. An isotope analysis method suitable for distinguishing between the two isotopes is described, for example, in Sieper et al., Rapid Commun. Mass Spectrom. (2006) 20: 2521-2527 and is based on the determination of the isotope ratios for, for example, C or N, which differ depending on whether a product originates from chemical (petroleum-based) or biotechnological, e.g., fermentative (plant-based) production. A process for producing OPS is considered to be a biotechnological, e.g., fermentative (plant-based) production process if, for example, the glucose used to cultivate the production strain originates from plant production, which also applies to the process described in Example 2. OPS is used in cysteine ​​metabolism, e.g.by Escherichia coli as a biosynthetic precursor of L-serine. The latter is produced by dephosphorylation of OPS. This reaction is enzymatically catalyzed by O-phospho-L-serine phosphatases (SerB, EC 3.1.3.3). It is known from the prior art that E. coli strains with suppressed SerB activity can accumulate OPS. A microorganism strain with suppressed SerB activity is thus characterized by the fact that it can no longer produce L-serine by dephosphorylation of OPS and, as a result, can no longer accumulate OPS. The process is preferably characterized in that the OPS used in the reaction is produced with a microorganism strain with suppressed activity of O-phospho-L-serine phosphatase (SerB enzyme), which belongs to the enzyme class EC 3.1.3.3.This means that in this case, a microorganism strain with suppressed SerB activity is used as the OPS production strain, whereby the suppression of SerB activity involves a genetic modification in the microorganism strain. The SerB activity of the genetically unmodified microorganism strain (wt strain) is set at 100%, and a microorganism strain with suppressed SerB activity is defined by the fact that it contains a lower SerB activity than the 100% activity in the wt strain, preferably a maximum of 20%, particularly preferably a maximum of 10%, and especially preferably 0% (inactivation of the serB gene) of the activity of the wild-type strain, which is set at 100%. The SerB activity still measurable in the modified microorganism strain, based on the activity in the wt strain as a percentage, is referred to as the residual activity.A microorganism strain with suppressed SerB activity is characterized by one or more of the following genetic alterations: - Deletion of the chromosomal gene encoding the enzyme SerB. - Introduction of a mutation in the chromosomal gene encoding the enzyme SerB to reduce the activity of the endogenous gene. - Substitution of the chromosomal gene encoding the enzyme SerB with a gene mutated to reduce the activity of the endogenous gene. - Introduction of a mutation in a regulatory region for the gene encoding the enzyme SerB to reduce endogenous enzyme activity. - Introduction of an antisense oligonucleotide complementary to the transcript of the gene encoding the enzyme SerB to inhibit mRNA translation.L-3-phosphoserine phosphatase enzyme activity (SerB activity) can be determined, as described in the prior art, by enzymatic release of phosphate from L-3-phosphoserine, with the released phosphate being quantitatively determined photometrically at 340 nm as a molybdate complex. The serB activity determined for the WT strain using this enzyme assay is set at 100% activity, and the residual activity for a microorganism strain with suppressed SerB activity is measured under identical conditions. The process according to the invention for producing L-cysteic acid is particularly preferably characterized in that the OPS used in the reaction is produced using a microorganism strain in which the chromosomal gene encoding the enzyme SerB has been deleted. This is also referred to as a knockout of the serB gene.In this case, the microorganism strain with suppressed SerB activity is preferably characterized in that the chromosomal nucleotide sequence of the serB gene, comprising the complete serB-cds, which encodes the enzyme SerB, as well as flanking sequences up to 1000 nt 5' upstream of the serB-cds, comprising the sequence of the serB promoter, and 1000 nt 3' downstream of the serB-cds, comprising the sequence of the serB terminator, is deleted. A particularly preferred deletion is the deletion of the serB-cds, which encodes the enzyme SerB, as described in Example 1. The microorganism strain with suppressed SerB activity is preferably selected from the families Corynebacteriaceae or Enterobacteriaceae, particularly preferably selected from the genera Corynebacterium, Pantoea or Escherichia and especially preferably selected from the species Pantoea ananatis or Escherichia coli.In particular, the microorganism strain with suppressed SerB activity for producing OPS for the reaction according to the invention is preferably the E. coli K12 W3110 strain. A microorganism strain with suppressed SerB activity is preferably characterized by serine auxotrophy, i.e. the strain cannot produce the amino acid L-serine for growth itself. The auxotrophy can be abolished by adding serine or glycine to the culture medium (growing medium), either as a pure substance or as a component of a complex media component such as yeast extract, peptone or tryptone or as a mixture of pure substance and complex media component. Preference is given to a mixture of pure substance selected from glycine and L-serine and complex media component, particularly preferably a mixture of glycine and complex media component. The addition of glycine to the growth medium is particularly preferred.The content of glycine as a pure substance in the culture medium is preferably 0.1 g / L to 10 g / L, particularly preferably 0.2 g / L to 5 g / L, and especially preferably 0.3 g / L to 2 g / L. According to the state of the art, the serB gene or part of the gene can be isolated and a foreign DNA can be cloned into the serB gene, thereby interrupting the open reading frame of the serB gene that defines the protein. A DNA construct suitable for the targeted inactivation of the serB gene can therefore consist of a 5' DNA segment that is homologous to the genomic serB gene, followed by a gene segment comprising the foreign DNA and, connected to this, a 3' DNA segment that is in turn homologous to the genomic serB gene. The region of the serB gene that is considered for homologous recombination cannot only include the region coding for O-phospho-L-serine phosphatase.The region in question can also include DNA sequences flanking the serB gene, namely in the 5' region before the start of the coding region (promoter of gene transcription) and in the 3' region after the end of the coding region (terminator of gene transcription). Alteration of these sequences through homologous recombination, just like alteration of the coding region, can lead to inactivation of the serB gene. The foreign DNA is preferably a selectable marker expression cassette. This consists of a gene transcription promoter that is functionally linked to the actual selectable marker gene and, if necessary, followed by a gene transcription terminator. In this case, the selectable marker also contains 5'- and 3'-flanking homologous sequences of the serB gene.The selection marker preferably contains 5'- and 3'-flanking homologous sequences of the serB gene, each at least 30 nucleotides long, particularly preferably at least 50 nucleotides long. The DNA construct for inactivating the serB gene can thus consist, starting from the 5' end, of a sequence homologous to the serB gene, followed by the expression cassette of the selection marker, e.g., selected from the class of antibiotic resistance genes, and followed by another sequence homologous to the serB gene.In a preferred embodiment, the DNA construct for inactivating the serB gene consists, starting from the 5' end, of a sequence homologous to the serB gene of at least 30 nucleotides in length, particularly preferably at least 50 nucleotides in length, followed by the expression cassette of the selection marker selected from the class of antibiotic resistance genes, and followed by another sequence homologous to the serB gene of at least 30 nucleotides in length, particularly preferably at least 50 nucleotides in length. The selection marker genes are generally genes whose gene product enables the parent strain to grow under selective conditions under which the original parent strain cannot grow. Preferred selection marker genes are selected from the group of antibiotic resistance genes, such asThe ampicillin resistance gene, the tetracycline resistance gene, the kanamycin resistance gene, the chloramphenicol resistance gene, or even the neomycin resistance gene. Other preferential selection marker genes enable parent strains with a metabolic defect (e.g., amino acid auxotrophies) to grow under selective conditions by correcting the metabolic defect. Finally, selection marker genes are also possible whose gene product chemically modifies and thus inactivates a compound that is inherently toxic to the parent strain (e.g., the gene for the enzyme acetamidase, which cleaves the compound acetamide, toxic to many microorganisms, into the nontoxic products acetate and ammonia). Among the selectable marker genes, the ampicillin resistance gene, the tetracycline resistance gene, the kanamycin resistance gene, and the chloramphenicol resistance gene are particularly preferred. The tetracycline resistance gene and the kanamycin resistance gene are especially preferred.Based on homologous recombination, there are also systems that, in addition to targeted gene inactivation, also offer the possibility of removing the selectable marker from the genome, thus making it possible to create double and multiple mutants. One such system is the so-called Lambda-Red technology, commercially available as the "Quick and Easy E. coli Gene Deletion Kit," based on the Red® / ET® technology from Gene Bridges GmbH (see "Technical Protocol, Quick & Easy E. coli Gene Deletion Kit, by Red® / ET® Recombination, Cat. No. K006, Version 2.3, June 2012" and the literature cited therein, e.g., Datsenko and Wanner, Proc. Natl. Acad. Sci. USA 97 (2000): 6640-6645). Example 1 of the present invention describes an example for the production of a microorganism strain with suppressed SerB activity by deletion of the serB gene. A strain with the red. ® / ET ®A microorganism strain produced using the technology and having suppressed SerB activity can be suitable for the extracellular production of OPS, as described, for example, in Example 2 of the present invention for the strain E. coli W3110-^serB. OPS can accumulate both intracellularly and extracellularly, whereby the amount of intracellularly accumulated OPS depends on the cultivation conditions (Steinfeld et al., see above). The culture conditions selected in Example 2 of the present invention enable the extracellular accumulation of OPS. The content of extracellular OPS is preferably at least 1 g / L, particularly preferably at least 3 g / L and especially preferably at least 6 g / L. An advantage of the described process for the biotechnological production of OPS is that OPS present extracellularly in a culture broth, such as that obtained, for example, in a cultivation as carried out in Example 2, can be used as an OPS source after separation of the particulate biomass, such as, for example,by centrifugation or filtration, preferably without further processing, purification, or isolation steps such as extraction, adsorption, ion exchange chromatography, precipitation, or crystallization, it can be used directly in the process according to the invention for producing L-cysteic acid. This procedure is particularly economical and avoids the isolation of OPS. The process for producing L-cysteic acid is therefore particularly preferably characterized in that OPS is used that originates from the cell culture supernatant of a microorganism strain with suppressed activity of O-phospho-L-serine phosphatase (SerB enzyme) belonging to the enzyme class EC 3.1.3.3.In a particularly preferred embodiment, the process for producing L-cysteic acid is characterized in that, in addition to the CS enzyme used in the reaction, the OPS used in the reaction is produced biotechnologically, particularly preferably by fermentation. The CS enzyme is preferably produced by culturing a microorganism strain of the Enterobacteriaceae family that heterologously expresses the CS enzyme. This microorganism strain is also referred to as a CS enzyme production strain, which consists of the host strain and a gene construct for expressing the CS gene. The process is preferably characterized in that the CS enzyme is produced by culturing a microorganism strain of the genus Escherichia, particularly preferably of the species Escherichia coli and especially preferably of the microorganism strain E. coli K12 JM105, which expresses the CS enzyme heterologously and especially preferably in enzymatically active form.A preferred gene construct for expressing the CS gene is an expression vector in plasmid form, particularly preferably the expression vector pCSma-pKKj disclosed in Example 3 (Fig. 3). Cysteate synthases are known as enzymes of coenzyme M biosynthesis in, for example, methanobacteria. The process for producing L-cysteic acid is preferably characterized in that the CS enzyme originates from Methanoscarcina acetivorans or the CS enzyme is a sequence homologous thereto; particularly preferably, the CS enzyme originates from Methanoscarcina acetivorans. The coding DNA sequence is particularly preferably SEQ ID NO: 3, which encodes a protein with the amino acid sequence SEQ ID NO: 4, or a nucleotide sequence homologous thereto. Homologous nucleotide sequences mean that the DNA sequences of these genes or DNA segments are at least 80%, preferably at least 90% and particularly preferably at least 95% identical.Preferred homologous nucleotide sequences are the sequences of the genes from Methanocella paludicola (NCBI Gene ID: 8682885), Methanosarcina barkeri (NCBI Gene ID: 24822660), and Methanoculleus marisnigri (NCBI Gene ID: 4845938), or homologous nucleotide sequences. The degree of DNA identity is determined using the "nucleotide blast" program, available at http: / / blast.ncbi.nlm.nih.gov / , which is based on the blastn algorithm. The predefined algorithm parameters for aligning two or more nucleotide sequences were used. The predefined general parameters are: Max target sequences = 100; Short queries = "Automatically adjust parameters for short input sequences"; Expect Threshold = 10; Word size = 28; Automatically adjust parameters for short input sequences = 0. The corresponding preset scoring parameters are: Match / Mismatch Scores = 1,-2; Gap Costs = Linear.In a preferred embodiment, the method is characterized in that the CS enzyme has the amino acid sequence specified in SEQ ID NO: 4 or a homologous amino acid sequence thereto, wherein an amino acid sequence homologous to SEQ ID NO: 4 has a sequence identity of at least 50%, preferably at least 70%, and particularly preferably at least 80% to SEQ ID NO: 4 and simultaneously exhibits cysteate synthase enzyme activity. Cysteate synthase enzyme activity can be detected as defined above in the CS activity test. Amino acid sequences of homologous CS enzymes can be found in the NCBI database (National Center for Biotechnology Information) using the search term "cysteate synthase" or using the "Protein BLAST" subprogram by entering the amino acid sequence SEQ ID NO: 4. Enzymes homologous to the CS enzyme from Methanoscarcina acetivorans are preferably selected from Methanocella paludicola (NCBI No.: WP_012900738.1), Methanolinea mesophila (NCBI No.: WP_245249687.1), Methanosarcina barkeri (NCBI No.: WP_011308449.1), and Methanoculleus marisnigri (NCBI No.: WP_011842967.1). The "Protein BLAST" search for genes for CS enzymes reveals homologous protein sequences from a variety of bacteria from the archaebacteria domain, including thermophilic organisms (growth at temperatures >50°C up to 110°C). Their enzymes typically also have activity optima >50°C. The invention also encompasses CS enzymes from the archaebacteria domain with activity optima >50°C. The "Protein BLAST" program, available at http: / / blast.ncbi.nlm.nih.gov / , is used to compare protein sequences. This program uses the blastp algorithm. The preset parameters were used as algorithm parameters for an alignment of two or more protein sequences.The preset general parameters are: Max target sequences = 100; Short queries = “Automatically adjust parameters for short input sequences”; Expect Threshold = 10; Word size = 3; Automatically adjust parameters for short input sequences = 0. The preset scoring parameters are: Matrix = BLOSUM62; Gap Costs = Existence: 11 Extension: 1; Compositional adjustments = Conditional compositional score matrix adjustment. The method is preferably characterized in that the CS enzyme is not a fusion protein. The term fusion protein means that the DNA sequence coding for a protein or part of a protein is fused in the reading frame in the laboratory with one or more DNA sequences coding for another protein or part of another protein, thus coding for a modified (extended) protein that does not occur in nature. The fused DNA sequences can be at the 5' end, the 3' end, orbe attached to both the 5' and 3' ends. It is also conceivable to insert the fused DNA sequence within the protein-coding sequence (e.g., as a link between two domains of a protein). The fusion protein is also referred to as a hybrid or hybrid enzyme. This means that the protein according to the invention with cysteate synthase enzyme activity is encoded only by the cds of the gene in question, and the CS-cds is not extended by additional sequences added to the CS-cds. A protein whose cds has been fused to a nucleotide sequence encoding a protein sequence that is cleaved off again during protein biosynthesis or post-translational modification, such as, for example, an export signal sequence that mediates protein secretion, is not encompassed by the term fusion protein. Within the scope of the invention, the term fusion protein always refers to the mature protein.In the context of the invention, the production of the CS enzyme by culturing a CS enzyme production strain refers to the production of the CS enzyme as an enzymatically active protein without refolding and preferably without recourse to expression as a fusion protein. Particular preference is given to the production of the CS enzyme from M. acetivorans by culturing a CS enzyme production strain as an enzymatically active protein without refolding and without recourse to expression as a fusion protein, wherein a host strain of the species Escherichia coli is used to produce the production strain. Particular preference is given to the production of the CS enzyme from M. acetivorans by culturing the production strain E. coli JM105 x pCSma-pKKj described in Example 3. The CS enzyme obtained by culturing the production strain can be used in the process according to the invention either as a culture broth that has not been further processed or as a cell suspension after re-isolation of the cells from the culture broth, e.g.by centrifugation or filtration. Furthermore, the CS enzyme can be used in the form of a cell homogenate after mechanical disruption of the cell suspension or in the form of chemically permeabilized cells (e.g. by chloroform) or as a cell extract after separation of particulate components from the cell homogenate or as an enzyme that has been purified, for example by chromatography. Preference is given to using the CS enzyme as culture broth that has not been further processed, particularly preferably fermenter broth, as a cell suspension after re-isolation of the cells from the culture broth or as a cell homogenate after mechanical disruption of the cell suspension or in the form of chemically permeabilized cells (e.g. by chloroform). Particular preference is given to using the CS enzyme as a cell suspension after re-isolation of the cells from the culture broth or as a cell homogenate, particularly preferably as a cell homogenate.In a preferred embodiment, after cultivating a CS enzyme production strain, CS enzyme is produced as a cell homogenate and used directly as CS enzyme in the biotransformation process according to the invention. A possible preferred embodiment is disclosed in Example 3 of the present invention. In principle, all conceivable salts of sulfurous acid are suitable for the reaction in the process for producing L-cysteic acid, including the known salts Na2SO3, K2SO3, (NH4)2SO3, NaHSO3 (or its anhydride Na2S2O5), or KHSO3. Also conceivable is the use of gaseous sulfur dioxide, the anhydride of sulfurous acid, which can be introduced into the reaction mixture, where it hydrates to the sulfurous acid H2SO3 and, depending on the pH, is in equilibrium with the deprotonated forms HSO3 and SO3. 2-is present. Preference is given to using Na2SO3, K2SO3, (NH4)2SO3, NaHSO3 (or its anhydride Na2S2O5), KHSO3, particularly preferably Na2SO3, NaHSO3 (or its anhydride Na2S2O5) and (NH4)2SO3, and especially preferably Na2SO3 and NaHSO3 (or its anhydride Na2S2O5). In a particularly preferred embodiment, Na2SO3 or NaHSO3 (or its anhydride Na2S2O5) is used as the salt of sulfurous acid in the process for producing L-cysteic acid. According to equation (1), phosphoric acid is released in stoichiometric amounts during the reaction of OPS to form L-cysteic acid, which can lead to a reduction in the pH of the mixture during the reaction. Since too low a pH impairs the activity of the CS enzyme, an excessive drop in the pH must be prevented. This can be done passively by adding a suitable highly concentrated buffer to the mixture or actively by using a measuring and control unit.Preference is given to active pH control (as described, for example, in Example 6) using a measuring and control unit which, if the pH deviates from the target value, readjusts the desired pH by metering in an alkali or acid (so-called pH-stat method). The reaction temperature is selected between 5°C and 80°C. A reaction temperature between 10°C and 60°C is preferred, more preferably between 15°C and 50°C, and especially preferably between 20°C and 40°C. The reaction can be carried out at a pH between 4.0 and 9.0, preferably at a pH between 5.0 and 8.5, more preferably at a pH between 5.5 and 8.0, and especially preferably at a pH between 6.0 and 7.5. Water is preferably used as the solvent for the process for producing L-cysteic acid. The process according to the invention for producing L-cysteic acid can be operated batchwise or continuously.In discontinuous operation (batch operation), all reactants are added to the mixture during the course of the reaction and the mixture is worked up after the reaction has ended. In continuous operation, the CS enzyme is introduced as the stationary phase, e.g. in a membrane reactor or immobilized on a support, and the substrate OPS and a salt of sulfurous acid are added as the mobile phase. The contact time of the mobile phase with the stationary phase is adjusted so that the substrate OPS can react with the salt of sulfurous acid to form the product L-cysteic acid. Discontinuous (batch) operation is preferred. The concentration of the salt of sulfurous acid in the mixture is preferably chosen so that it is present in at least an equimolar concentration to OPS, preferably at least in a 1.5-fold molar excess, more preferably in at least a 2-fold molar excess and especially preferably in at least a five-fold molar excess to OPS.The OPS concentration in the batch is preferably at least 80 mg / L, more preferably at least 1 g / L, and especially preferably at least 5 g / L. The process for producing L-cysteic acid is preferably characterized in that the molar yield of L-cysteic acid, based on the molar amount of OPS used, is at least 60%, more preferably at least 80%, and especially preferably at least 90%. The process according to the invention is suitable for use on an industrial scale. A batch volume of >10 ml is preferred, more preferably >1 L, and especially preferably >100 L.Contrary to the prior art, it was surprisingly found that recombinantly heterologously produced CS enzyme in a CS enzyme production strain is enzymatically active without refolding (renaturation) and preferably without recourse to a fusion partner in a cell homogenate and is suitable for the efficient production of L-cysteic acid in a previously unknown biotransformation. For this purpose, for example, fermentatively produced OPS from the cell culture supernatant of the cultivation of an OPS production strain with preferably suppressed activity of the SerB enzyme or commercially available OPS can be reacted with a salt of sulfurous acid according to equation (1). Also preferred is a process for the production of taurine, characterized in that the L-cysteic acid produced according to the invention is decarboxylated.The decarboxylation of L-cysteic acid to taurine takes place according to equation (2): (2) L-cysteic acid -> taurine + CO2 The process for producing taurine is particularly preferably characterized in that the L-cysteic acid produced in the process according to the invention is used directly, i.e. without further processing, purification or isolation steps, for the production of taurine, as disclosed, for example, in Examples 8 and 9 of the present invention. The decarboxylation of L-cysteic acid to taurine can take place chemically or enzymatically catalyzed in a biotransformation. Thermal decarboxylation at high temperatures under metal catalysis, which is not regarded as sustainable, is known but suffers from the fact that it is energy-intensive and produces a high proportion of by-products. The decarboxylation reaction is preferably a biotransformation, whereby L-cysteic acid is enzymatically decarboxylated to taurine.For the production of taurine by enzymatic decarboxylation, the L-cysteic acid produced in the process according to the invention can be used directly as a reaction mixture without further processing steps. However, it is also possible to separate particulate biomass from the reaction mixture before the enzymatic decarboxylation, e.g., by centrifugation, or to previously isolate L-cysteic acid from the reaction mixture. Preference is given to the direct use of the reaction mixture containing L-cysteic acid or to the use of the reaction mixture containing L-cysteic acid after separation of particulate biomass. Particular preference is given to the direct use of the reaction mixture containing L-cysteic acid without further processing steps, as disclosed, for example, in Example 8 for the production of taurine.Enzymes from the class of L-cysteine ​​sulfinic acid decarboxylases (CSAD, EC 4.1.1.29), aspartate 1-decarboxylases (EC 4.1.1.11), or glutamate decarboxylases (EC 4.1.1.15) are suitable for the enzymatically catalyzed decarboxylation of L-cysteine ​​acid to taurine according to equation (2). The process for producing taurine is preferably characterized in that the decarboxylation is carried out using a cysteine ​​sulfinic acid decarboxylase (CSAD enzyme) belonging to the enzyme class EC 4.1.1.29. CSAD enzymes are known to decarboxylate L-cysteine ​​sulfinic acid to hypotaurine according to equation (3). (3) L-cysteine ​​sulfinic acid -> hypotaurine + CO2. To varying degrees, these enzymes are also capable of decarboxylating L-cysteine ​​acid as a substrate to taurine. As shown in Examples 8 and 9, for example, the CSADcc enzyme from Cyprinus carpio (carp) is suitable for decarboxylating L-cysteic acid to taurine according to equation (2).CSAD enzymes are found mainly in metazoa (multicellular animals), including mammals such as humans (Homo sapiens), cattle (Bos taurus), rats (Rattus norvegicus), and mice (Mus musculus), but also in fish such as carp (Cyprinus carpio). Enzymes with CSAD activity can also be found in unicellular organisms such as algae, e.g. from the genus Synechococcus, as well as in bacteria and fungi. CSAD enzymes from mammals are preferred, selected from humans (Homo sapiens), cattle (Bos taurus), rats (Rattus norvegicus), and mice (Mus musculus), as well as from fish such as carp (Cyprinus carpio). CSAD enzymes from humans (Homo sapiens), rats (Rattus norvegicus), and cars (Cyprinus carpio) are particularly preferred. In particular, the CSAD enzyme comes from the carp (Cyprinus carpio) and is referred to as CSADcc.The DNA sequence underlying the CSADcc amino acid sequence is accessible in the NCBI database under Genbank Sequence ID: AB220585.1 (cds: nt 82–1584). A codon-optimized CSADcc-cds DNA sequence is preferably derived from the corresponding amino acid sequence for expression in the specifically selected microorganism (such as E. coli) (e.g., given for E. coli in SEQ ID NO: 5, nt 31–1530, encoding a protein with the amino acid sequence SEQ ID NO: 6). Publicly available software programs are available for codon optimization, such as the Eurofins Genomics GENEius software used in Example 7. The process for producing taurine is preferably characterized in that the amino acid sequence of the CSAD enzyme is SEQ ID NO: 6. Preferably, the CSAD enzyme, particularly preferably CSADcc, is produced recombinantly by a microorganism production strain.The production of the CSAD enzyme by recombinant production in an E. coli production strain is disclosed, for example, in Example 7. The CSAD-cds is cloned in a known manner into an expression vector, e.g., the vector pKKj (see Example 3), and a gene construct, e.g., pCSADcc-pKKj (Fig. 4), is produced. To produce a production strain, the gene construct containing the CSAD-cds, e.g., pCSADcc-pKKj, is transformed in a likewise known manner into a microorganism host strain, e.g., the E. coli JM105 strain, and the resulting production strain, e.g., E. coli JM105 x pCSADcc-pKKj, is used in a likewise known manner to produce the CSAD enzyme. The CSAD enzyme can be produced for laboratory purposes on a shake flask scale (as described, for example, in Example 7) or, in a known manner, by fermentation. CSAD enzymes contain pyridoxal phosphate (PLP, CAS No. 54-47-7) as a cofactor.Supplementing the culture medium or biotransformation approaches for the conversion of L-cysteic acid to taurine with PLP therefore offers an opportunity for process improvement. Since PLP belongs to the B6 vitamin family, supplementation with other members of the vitamin B6 family, such as pyridoxine (CAS No. 65-23-6), pyridoxal (CAS No. 66-72-8), or pyridoxamine (CAS No. 85-87-0), is also suitable for process improvement. The CSAD enzyme, preferably CSADcc, obtained by culture in shake flasks or by fermentation can be used either as a culture broth without further processing or as a cell suspension after re-isolation of the cells, for example by centrifugation. Furthermore, the CSAD enzyme, preferably CSADcc, can be used in the form of a cell homogenate after mechanical disruption of the cell suspension or in the form of chemically permeabilized cells (e.g.by chloroform) or as a cell extract after separation of particulate components from the cell homogenate or as an enzyme purified by chromatography, for example. Preference is given to using the CSAD enzyme as a cell suspension after re-isolation of the cells from the culture broth, as described, for example, in Examples 7 and 8. The biotransformation of L-cysteic acid to taurine by the CSAD enzyme is carried out under pH and temperature conditions that enable efficient decarboxylation of L-cysteic acid to taurine. A pH range between 5.0 and 9.0 and a temperature range between 20°C and 70°C for the biotransformation is preferred. The biotransformation for the production of taurine from L-cysteic acid can be carried out batchwise or continuously.In batch operation, all reactants are added to the mixture during the course of the reaction, and the mixture is processed after the reaction has ended. In continuous operation, the CSAD enzyme is introduced as the stationary phase, e.g., in a membrane reactor or immobilized on a support, and the substrate L-cysteic acid is added as the mobile phase. The contact time between the mobile phase and the stationary phase is adjusted so that the substrate L-cysteic acid can react to form the product taurine. Batch operation is preferred. The L-cysteic acid concentration in the biotransformation for the production of taurine is preferably at least 80 mg / L, more preferably at least 1 g / L, especially preferably at least 5 g / L.The process for producing taurine is preferably characterized in that the molar yield of taurine, based on the molar amount of L-cysteic acid used, is at least 60%, preferably at least 80%, particularly preferably at least 90%, and especially preferably at least 95%. The process steps for producing L-cysteic acid (biotransformation 1) and for producing taurine preferably proceed sequentially, i.e. one after the other. In an alternatively preferred embodiment, the process for producing taurine is characterized in that all process steps take place in one reaction batch. If all process steps take place in one reaction batch, this is also referred to as a one-pot process or a one-pot reaction.Example 9 of the present invention discloses a possibility of carrying out such a one-pot reaction, in which the inventive biotransformation of OPS to L-cysteic acid according to equation (1) and the biotransformation of L-cysteic acid to taurine according to equation (2) take place simultaneously, i.e. in one reaction batch, wherein OPS is reacted with a sulfite (salt of sulfurous acid) in the presence of the CS and CSAD enzymes. In the first reaction, L-cysteic acid is formed, which is decarboxylated "in situ" by the CSAD enzyme to taurine. The product distribution of L-cysteic acid and taurine is determined by the activity of the CS enzyme in relation to that of the CSAD enzyme. With a sufficient dosage of the CSAD enzyme, the L-cysteic acid can be quantitatively converted to taurine.Preferred is a process in which the OPS used is converted to L-cysteic acid and taurine, wherein the total molar yield of L-cysteic acid and taurine is more than 60%, particularly preferably more than 70%, and especially preferably more than 80%. Carrying out the process for producing L-cysteic acid and decarboxylating it to taurine in one reaction batch is of particular economic interest. It is also conceivable that, in the sense of a metabolic engineering approach, the genes for cysteate synthase, preferably CSma, and L-cysteine ​​sulfinic acid decarboxylase, preferably CSADcc, are expressed in the OPS production strain, and taurine is produced by cultivating such a production strain in the presence of a sulfur source, preferably a sulfite (salt of sulfurous acid).It is also conceivable that the genes for cysteate synthase, preferably CSma, and L-cysteine ​​sulfinic acid decarboxylase, preferably CSADcc, are expressed together in one strain and that the cells from the culture of this strain are reacted with OPS in the presence of a sulfite, whereby taurine is formed as the end product. A biotransformation process for the production of taurine is preferred in which the process components OPS, the CS enzyme and the CSAD enzyme are produced separately. Taurine can either be used directly without further processing steps or can be enriched or purified using known methods. Such methods are known to the person skilled in the art, for example from processes for the isolation of amino acids. They include, for example, filtration, centrifugation, extraction, adsorption, ion exchange chromatography, precipitation and crystallization.The invention further relates to the use of the resulting L-cysteic acid in a process for producing taurine. Compared to the known chemical processes for producing taurine from fossil raw materials, the use of the L-cysteic acid produced in the process according to the invention for producing taurine enables a biotechnological process from plant raw materials. Due to the sustainable production process, a biotechnological process for producing taurine is of particular interest for applications in the food, feed, or cosmetics sectors. The invention is further illustrated by the following examples, without being limited by them.

[0002] Example 1: Production of a serB deletion mutant in Escherichia coli The strain Escherichia coli K12 W3110 was used (available under strain number DSM 5911 from the DSMZ Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH). The target of gene inactivation was the coding sequence of the serB gene from E. coli. The DNA sequence of the cds of the serB gene from E. coli K12 (SEQ ID NO: 1, nt 67 to nt 1032), coding for a protein with the amino acid sequence SEQ ID NO: 2, is accessible in the NCBI (National Center for Biotechnology Information) gene database with the Gene ID 948913. The E. coli serB gene was ® / ET ® -technology from Gene Bridges GmbH, as detailed below (described in the user manual of the “Quick and Easy E. coli Gene Deletion Kit”, see “Technical Protocol, Quick & Easy E. coli Gene Deletion Kit, by Red ® / ET ®Recombination, Cat. No. K006, Version 2.3, June 2012 and literature cited therein, e.g. Datsenko and Wanner, Proc. Natl. Acad. Sci. USA 97 (2000): 6640-6645). The plasmids pKD13, pKD46 and pCP20 were used for this purpose: - The 3.4 kb plasmid pKD13 (Fig. 1) is disclosed in the “GenBank” gene database under the accession number AY048744.1. - The 6.3 kb plasmid pKD46 (Fig. 2) is disclosed in the “GenBank” gene database under the accession number AY048746.1. - The 9.4 kb plasmid pCP20 is disclosed in Cherepanov and Wackernagel, Gene 158 (1995): 9-14. To inactivate the serB gene in E. coli W3110 by homologous recombination with the Lambda Red system, the following steps were carried out: 1. E. coli W3110 was transformed with the plasmid pKD46 (so-called “Red Recombinase” plasmid, Fig. 2) and an ampicillin-resistant clone was isolated, designated W3110 x pKD46. 2. A serB-specific DNA fragment suitable for its inactivation was generated in a PCR reaction (“PhusionTM High- Fidelity“ DNS-Polymerase, Thermo Scientific TM) using DNA from plasmid pKD13 (Fig. 1) and the primers serb-1f (SEQ ID NO: 7) and serb-2r (SEQ ID NO: 8). The PCR reaction produced a 1.4 kb PCR product containing a 30 nt DNA segment at both the 5' and 3' ends that was specific for the serB gene from E. coli W3110. In addition, the PCR product contained the expression cassette of the kanamycin resistance gene contained in pKD13 and, flanking the 5' and 3' ends of the kanamycin expression cassette, so-called "FRT direct repeats" (referred to as "FRT1" and "FRT2" in Fig. 1), short DNA segments that served as recognition sequences for the "FLP recombinase" (contained on the plasmid pCP20) in a later step to remove the antibiotic marker kanamycin. Primer serb-1f contained 30 nucleotides (nt) from the 5' region of the serB gene (nt 67-96 in SEQ ID NO: 1) and, attached to it, 20 nt specific for the plasmid pKD13 (referred to as "pr-1" in Fig. 1).Primer serb-2r contained 30 nt from the 3' region of the serB gene (nt 1006–1035 in SEQ ID NO: 1, in reverse complementary form) and, connected to it, 20 nt specific for the plasmid pKD13 (designated "pr-2" in Fig. 1). 3. The 1.4 kb PCR product was isolated and treated with the restriction endonuclease Dpn I, which is familiar to those skilled in the art and only cuts methylated DNA, to remove residual pKD13 plasmid DNA. Unmethylated DNA from the PCR reaction was not degraded. 4. The 1.4 kb PCR product, specific for the serB gene and containing an expression cassette for the kanamycin resistance gene, was transformed into E. coli W3110 x pKD46, and kanamycin-resistant clones were isolated on LBkan-glycine plates at 30°C. LBkan-glycine plates contained LB medium (10 g / L tryptone from GIBCO). TM, 5 g / L yeast extract from BD Biosciences, 5 g / L NaCl), 1.5% agar, 15 mg / L kanamycin (Sigma-Aldrich), and 1 g / L glycine (Sigma-Aldrich). 5. Four of the resulting kanamycin-resistant clones were purified on LBkan-glycine plates (i.e., isolating a clone by singulation) and checked in a PCR reaction whether the kanamycin resistance cassette had been correctly integrated into the serB gene. The sequence used for the PCR reaction (“Phusion TM “High-Fidelity” DNA polymerase, Thermo Scientific TMThe genomic DNA used was isolated from cells grown with kanamycin-resistant clones of E. coli W3110 x pKD46 in LBkan-glycine medium (10 g / L tryptone, 5 g / L yeast extract, 5 g / L NaCl, 15 mg / L kanamycin, 1 g / L glycine) using a DNA isolation kit (Qiagen). Genomic DNA of the wild-type E. coli W3110 strain served as a control. The primers used for the PCR reaction were serb-3f (SEQ ID NO: 9, 5'-flanking the serB gene, nt 1-22 in SEQ ID NO: 1) and serb-4r (SEQ ID NO: 10, 3'-flanking the serB gene, nt 1066-1085 in SEQ ID NO: 1, in reverse complementary form). E. coli W3110 wild-type DNA yielded a 1.1 kb DNA fragment in the PCR reaction, as expected for the intact gene. The four kanamycin-resistant clones tested, however, yielded a DNA fragment of approximately 1.6 kb in the PCR reaction, as expected if the 1.4 kb PCR product had been integrated into the serB gene at the sites defined by primers serb-1f and serb-2r.This result demonstrated that the kanamycin resistance gene had been successfully integrated at the serB gene locus, thus inactivating the serB gene. A clone with an inactivated serB gene was selected and treated at 42°C to remove the temperature-sensitive plasmid pKD46, rendering the strain ampicillin-sensitive again. The strain was designated W3110-^serB::kan. 6. To eliminate the kanamycin selection marker, W3110-^serB::kan was transformed with the plasmid pCP20, and transformants were selected at 30°C. The 9.4 kb vector pCP20 is disclosed in Cherepanov and Wackernagel (1995), Gene 158: 9-14. The vector pCP20 contains the FLP recombinase gene. FLP recombinase recognizes the FRT sequences flanking the expression cassette of the kanamycin resistance gene and causes the removal of the kanamycin expression cassette. For this purpose, the clones obtained at 30°C were incubated at 37°C.Under these conditions, expression of FLP recombinase was induced, and replication of the pCP20 vector was inhibited. This step resulted in clones in which the serB gene had been inactivated and which were again sensitive to kanamycin (so-called "curing" of the antibiotic selection marker). The removal of the kanamycin cassette from the genome of the ^serB mutants allows the introduction of further mutations to create double or multiple mutants. W3110- ^serB::kan was again kanamycin sensitive after treatment with the pCP20 plasmid, which was verified as follows: - by plating on LB-glycine and LBkan-glycine plates: Growth on LB-glycine plates was positive, while no growth was observed on LBkan-glycine plates, indicating the successful removal of the kanamycin cassette from the genome.- by PCR reaction: For this purpose, genomic DNA was isolated from the kanamycin-sensitive clones (Qiagen DNA isolation kit) and in a PCR reaction (“Phusion. TM “High-Fidelity” DNA polymerase, Thermo Scientific TM) with the primers serb-3f (SEQ ID NO: 9) and serb-4r (SEQ ID NO: 10). E. coli W3110 wild-type DNA yielded a DNA fragment of 1.1 kb in the PCR reaction, as expected for the intact serB gene. The kanamycin-sensitive clone, on the other hand, yielded a DNA fragment of approximately 250 nt in the PCR reaction, which corresponded to the expected size of the 5' and 3' fragments of the inactivated serB gene remaining after homologous recombination. The strain isolated from this step was designated E. coli W3110-^serB. This strain was distinguished by the fact that it contained an inactivated serB gene and was again sensitive to the antibiotic kanamycin. Example 2: Production of OPS Shake-flask production: OPS was produced by growing the E. coli W3110-^serB strain in a shake flask. For comparison, the OPS production of the WT E. coli W3110 strain was investigated.As a preculture for the shake flask cultivation, 3 ml each of LB-glycine medium (10 g / L tryptone, 5 g / L yeast extract, 10 g / L NaCl, 0.1 g / L glycine) was inoculated with the strains E. coli W3110 and E. coli W3110-^serB and incubated at 30°C and 135 rpm for 16 h in a shaker. Main culture: Subsequently, a portion of each preculture was transferred to a 300 ml Erlenmeyer flask (with baffle) containing 30 ml of SM1 medium containing 15 g / L glucose, 5 mg / L vitamin B1 (Sigma-Aldrich), 0.1 g / L each of the amino acids L-isoleucine, D,L-methionine, L-threonine, and 0.5 g / L glycine (all Sigma-Aldrich). Composition of SM1 medium: 12 g / L K2HPO4, 3 g / L KH2PO4, 5 g / L (NH4)2SO4, 0.3 g / L MgSO4x 7 H2O, 0.015 g / L CaCl2x 2 H2O, 0.002 g / L FeSO4x 7 H2O, 1 g / L Na3Citrate x 2 H2O, 0.1 g / L NaCl; 1 ml / L trace element solution. Composition of the trace element solution: 0.15 g / L Na2MoO4x 2 H20, 2.5 g / L H3BO3, 0.7 g / L CoCl2x 6 H20, 0.25 g / L CuSO4x 5 H20, 1.6 g / L MnC12 x 4 H20, 0.3 g / L ZnSO4 x 7 H20.The main cultures were inoculated with enough preculture to achieve an initial cell density OD. 600 / ml (optical density of the main culture, measured at 600 nm) of 0.3 / ml each. From this point, the 30 ml batches were incubated for 24 h at 30°C and 135 rpm. After 24 h, samples were taken and the cell density OD 600 / ml and the OPS content in both the culture supernatant and the cell pellet were determined. For this purpose, 2 ml of the cell culture were centrifuged for 5 min at 13,000 rpm (Heraeus TM Fresco TM 21 centrifuge). The cell culture supernatants were analyzed directly for OPS content by HPLC. The cell pellets were resuspended in 2 ml of H2O each, and cell extracts were prepared using the FastPrep-24 cell homogenizer. TM5G from MP Biomedicals was used. Two 1 ml portions of the cell pellets suspended in water were lysed in 1.5 ml tubes containing glass beads (“Lysing Matrix B”) prepared by the manufacturer (3 x 20 sec at a shaking frequency of 6000 rpm with a 30 sec break between each interval). The resulting cell homogenates were combined and centrifuged for 5 min at 13000 rpm to produce a cell extract. The cell extract was analyzed for OPS content by HPLC. The results are summarized in Table 1. Table 1: Cultivation of the E. coli W3110 and E. coli W3110-^serB strains and HPLC analysis of the OPS content of the cell culture supernatant and cell extract. HPLC analysis of OPS, L-cysteic acid, and taurine: For the quantitative determination of the compounds analyzed in the examples, an HPLC method calibrated for OPS, L-cysteic acid, and taurine was used. All reference substances used for calibration were commercially available (Sigma-Aldrich). An Agilent HPLC instrument, Model 1260 Infinity II, was used. It was equipped with a pre-column derivatization with o-phthalaldehyde (OPA derivatization) from the same manufacturer, a process known from the analysis of amino acids. The HPLC instrument was equipped with a fluorescence detector for the detection of the OPA-derivatized products of OPS, L-cysteic acid, and taurine. The detector was set to an excitation wavelength of 330 nm and an emission wavelength of 450 nm. A Luna® C18(2) column from Phenomenex, length 250 mM, inner diameter 4.6 mm, particle size 5 µm, heated to 40°C in the column oven, was also used.Mobile phase A: 25 mM Na phosphate, pH 6.0. Mobile phase B: methanol. The separation was carried out in gradient mode: 0–10 min, 1%–15% mobile phase B, followed by 15 min of 15% mobile phase B, at a flow rate of 1.0 ml / min. Retention time of L-cysteic acid: 6.95 min. Retention time of OPS: 7.65 min. Retention time of taurine: 21.9 min. Production of OPS by fermentation: OPS was produced by fermentation of the E. coli W3110-^serB strain. Preculture 1: 20 ml of LB-glycine medium was inoculated with the E. coli W3110-^serB strain in a 100 ml Erlenmeyer flask and incubated for 7 h on a shaker (150 rpm, 32°C). Preculture 2: Subsequently, preculture 1 was completely transferred into 100 ml of SM1 medium supplemented with 10 g / L glucose, 10 g / L yeast extract, 0.3 g / L L-methionine, 1 g / L glycine, and 5 mg / L vitamin B1. The culture was incubated in a 1-L Erlenmeyer flask at 32°C for 17 h at 150 rpm (Infors chest shaker). After this incubation, the cell density (OD) was 1000 µL.600 / ml at 5.7 / ml. Main culture: The fermentation was carried out in a fermenter of the type “DASGIP ®Parallel Bioreactor Systems for Microbiology" from Eppendorf. Culture vessels with a total volume of 1.8 l were used. The fermentation medium (600 ml) contained 10 g / L glucose, 5 g / L yeast extract, 5 g / L (NH4)2SO4, 5 g / L KH2PO4, 0.5 g / L NaCl, 0.225 g / L CaCl2 x 2 H2O, 1.2 g / L MgSO4 x 7 H2O, 0.075 g / L FeSO4 x 7 H2O, 1 g / L Na3 citrate x 2 H2O, 1 g / L glycine, 1 g / L L-threonine, 0.018 g / L vitamin B1, 0.09 g / L vitamin B6, and 10 ml of trace element solution (see shake flask cultivation). The pH value in the fermenter was initially adjusted by A 25% NH4OH solution was pumped in to adjust the pH to 7.0. During fermentation, the pH was maintained at 7.0 by automatic correction with 25% NH4OH or 4 M H3PO4. Foam control was achieved by automatically adding 4% v / v Struktol J673 in H2O (Schill & Seilacher). For inoculation, 60 ml of preculture 2 was pumped into the fermenter vessel. The initial volume was thus approximately 660 ml.The cultures were initially stirred at 400 rpm and aerated with compressed air purified through a sterile filter at an aeration rate of 2 vvm (volume of air per volume of culture medium per minute). Under these initial conditions, the oxygen probe was calibrated to 100% saturation before inoculation. The target value for O2 saturation during fermentation was set to 30%. Once the O2 saturation fell below the target value, a regulation cascade was initiated to return the O2 saturation to the target value. First, the gas supply was continuously increased (to a maximum of 5 vvm) and then the stirring speed (to a maximum of 1,600 rpm). The fermentation was carried out at a temperature of 32°C. As soon as the glucose content in the fermenter had dropped from an initial 10 g / L to approximately 2 g / L, a 56% (w / w) glucose solution was continuously added.The feed rate was adjusted so that the glucose concentration in the fermenter no longer exceeded 2 g / L. Glucose was determined using a glucose analyzer from YSI (Yellow Springs, Ohio, USA). 23 h after the start of fermentation, the fermentation mixture was supplemented with 3.5 ml of a 200 g / L glycine solution in H2O. The fermentation time was 53 h. Samples were taken from the fermentation mixture 23 h, 30 h, 47 h, and 53 h after the start of fermentation, and the cell density (OD) of an aliquot was determined. 600 / ml. A further aliquot was incubated for 5 min at 80°C, centrifuged, and the OPS content of the cell culture supernatant was determined by HPLC. Cell density and OPS content are summarized in Table 2. Table 2: Time course of cell density and OPS content in the fermentation of the E. coli W3110- ^serB strain. Example 3: Production of CSma enzyme. Cysteate synthase from Methanosarcina acetivorans (CSma) was used. The amino acid sequence of the CSma enzyme is available in the NCBI database under accession ID WP_048066469. A codon-optimized DNA sequence for expression in E. coli was derived from the amino acid sequence (publicly available Eurofins Genomics GENEius software) and synthetically produced (Eurofins Genomics). The synthetically produced DNA had the sequence disclosed in SEQ ID NO: 3 and contained the cds of the gene, hereinafter referred to as CSma-cds (SEQ ID NO: 3), encoding a protein with the amino acid sequence disclosed in SEQ ID NO: 4 and designated CSma. For cloning purposes, the synthetically produced DNA contained an EcoRI site at the 5' end and a HindIII site at the 3' end. To produce the vector pCSma-pKKj suitable for recombinant expression of CSma-cds (Fig.3) The synthetically produced DNA was cleaved with EcoRI and HindIII and cloned in a known manner as an EcoRI / HindIII fragment into the EcoRI and HindIII-cleaved vector pKKj. The expression vector pKKj, disclosed in EP2670837A1 (Wacker application), is a derivative of the expression vector pKK223-3. The DNA sequence of pKK223-3 is disclosed in the GenBank gene database under accession number M77749.1. Approximately 1.7 kb was removed from the 4.6 kb plasmid (bp 262–1947 of the DNA sequence disclosed in M77749.1), resulting in the 2.9 kb expression vector pKKj. For expression of the CSma-cds in E. coli, the vector pCSma-pKKj was transformed in a known manner into the E. coli K12 JM105 strain. The E. coli K12 JM105 strain is commercially available from the DSMZ German Collection of Microorganisms and Cell Cultures GmbH under strain number DSM 3949. Clones of the transformation were selected on LBamp plates.LBamp contained 10 g / L tryptone, 5 g / L yeast extract, 5 g / L NaCl, 15 g / L agar, and 100 mg / L ampicillin (Sigma-Aldrich). One clone was selected and cultured in a shake flask. The CSma-producing strain was designated E. coli JM105 × pCSma-pKKj. Expression of CSma-cds occurred in E. coli JM105 × pCSma-pKKj in a known manner under the control of the IPTG-inducible tac promoter (IPTG: isopropyl-ß-thiogalactoside, Sigma-Aldrich) functionally linked to CSma-cds. Shake flask culture: A preculture of E. coli JM105 x pCSma-pKKj was prepared in LBamp medium (grown overnight at 37°C and 120 rpm using an Infors chest shaker). Two ml of preculture (OD 100 µl) was added. 6003.4 / ml) were used as inoculum of a main culture (0.3 L Erlenmeyer flask) of 50 ml SM1 medium (Example 2) supplemented with 15 g / L glucose; 5 g / L peptone (Oxoid); 2.5 g / L yeast extract; 0.005 g / L vitamin B1 (Sigma-Aldrich); 5 mg / L pyridoxal phosphate (PLP, Sigma-Aldrich), and 100 mg / L ampicillin. The main culture was shaken in a chest shaker (Infors) at 30°C and 140 rpm. After 4 h of incubation, a cell density OD 600 of 2.0 was reached. Then, the inducer IPTG (Sigma-Aldrich, 0.4 mM final concentration) was added, and culture was continued for another 20 h in a chest shaker (Infors) at 30°C and 140 rpm. At the end of culture, the cell density OD 6003.1 / ml. The cells from the shake flask culture were isolated by centrifugation (10 min, 15,000 rpm, Sorvall Centrifuge RC5C, equipped with an SS34 rotor). To prepare a cell suspension, the cell pellet from 50 ml of shake flask culture was resuspended in 2 ml of 100 mM K-phosphate, pH 7.0; 100 mM KCl (KPi7.0 buffer) and used to prepare a cell homogenate. The preparation of a cell homogenate using the FastPrep-24™ 5G cell homogenizer from MP Biomedicals was carried out as described in Example 2. The resulting cell homogenate (2 ml volume) was used without further processing for the biotransformation of OPS to L-cysteic acid (Example 5). The protein content of the cell homogenate was determined using a Qubit 3.0 fluorometer from Thermo Fisher Scientific using the "Qubit ®Protein Assay Kits" according to the manufacturer's instructions. The protein content of the cell homogenate from the shake flask culture was 5.3 mg / ml. Example 4: Production of L-cysteic acid from commercially available OPS and Na2SO3 by biotransformation with CSma enzyme Two batches were carried out in parallel: Batch 1: 8.15 ml of KPi7.0 buffer were placed in a 100 ml Erlenmeyer flask, and 1 ml of a 0.2 M solution of Na2SO3 in KPi7.0 buffer, 0.5 ml of CSma cell homogenate from the shake flask culture (Example 3), and 350 µl of a 0.2 M solution of OPS (Sigma-Aldrich) in KPi7.0 buffer were added successively. The batch volume was 10 ml. Batch 2: The batch (comparison batch without Na2SO3) had the same composition as Batch 1. Instead of the The Na2SO3 solution was mixed with 21 ml of KPi7.0 buffer. Both mixtures were incubated in a chest shaker (Infors) at 30°C and 140 rpm.After 1 h, 2 h, and 4 h, 1 ml of each sample was incubated for 5 min at 80°C, centrifuged, and the supernatant analyzed by HPLC. The time course of L-cysteic acid production from OPS is shown in Table 3. Table 3: Time course of L-cysteic acid production by biotransformation of OPS and Na2SO3 with CSma-containing cell homogenate. Example 5: Production of L-cysteic acid from OPS-containing shake flask culture supernatant and Na2SO3 by biotransformation with CSma enzyme. 9 ml of cell culture supernatant from shake flask culture of E. coli W3110-^serB (Example 2) with an OPS content of 113.6 mg / L were placed in a 100 ml Erlenmeyer flask. 0.3 ml of 3 M KCl, 0.5 ml of 0.2 M Na2SO3 in KPi7.0 buffer, and 1 ml of CSma cell homogenate from shake flask culture (Example 3) were added. The mixture volume was 10.8 ml. The mixture was incubated in a chest shaker (Infors) at 30°C and 140 rpm. At the beginning and after 6 hours of incubation, 1 ml of the mixture was incubated for 5 minutes at 80°C, centrifuged, and the supernatant was analyzed by HPLC for the content of OPS and L-cysteic acid. The time course of the reaction is summarized in Table 4. The molar yield of L-cysteic acid, based on the molar amount of OPS used, was 97.6% (Table 4).4: Time course of the production of L-cysteic acid from OPS-containing cell culture supernatant and Na2SO3 by catalysis with CSma-containing cell homogenate. Example 6: Preparative production of L-cysteic acid by biotransformation of OPS at constant pH. OPS substrate: 10 ml of fermenter broth from the fermentation of E. coli W3110-^serB strain (Example 2) was centrifuged (10 min at 15,000 rpm, Sorvall RC5C centrifuge equipped with an SS34 rotor), and the OPS content in the fermentation supernatant was determined by HPLC. The OPS content was 5.6 g / L. CSma homogenate: Cell homogenate of E. coli JM105 x pCSma-pKKj strain was prepared from 2 x 50 ml shake flask cultures as described in Example 3. The homogenate was supplemented with 15 µl of 500 mg / L PLP. The total volume of the homogenate was 4 ml. Biotransformation approach: A double-walled, downwardly tapered 50 ml thermostattable reaction vessel (accessory for the TitroLine alpha titrator, Schott) was connected to a thermostat (Lauda) via a hose connection and heated to 30°C.The reaction mixture contained 6 ml of OPS-containing fermentation supernatant with an OPS content of 5.6 g / L, 4 ml of CSma homogenate, 0.2 ml of 3 M KCl, 0.1 ml of 0.1 M DTE (dithioerythrol, Sigma-Aldrich), and 0.3 ml of a 1 M solution of Na2SO3 in KPi 7.0 buffer. The reaction volume was 10.6 ml. The OPS concentration in the mixture was 17.1 mM (0.18 mmol OPS in 10.6 ml of reaction volume). The mixture was stirred with a magnetic stirrer. The mixture was further equipped with a pH electrode (Mettler Toledo) connected to a pH control unit (TitroLine alpha titrator, Schott) operated in pH-stat mode according to the manufacturer's instructions. Under pH-stat conditions, the pH in the reaction vessel was kept constant at the set pH 7.0 throughout the reaction by adding 0.5 M NaOH from a burette connected to the control unit. The reaction time was 4 h.Since 0.5 M NaOH was added from the burette to the mixture to maintain a constant pH of 7.0, the mixture volume after a reaction time of 4 h was 13.0 ml. Two and four hours after the start of the reaction, 50 µl aliquots of the mixture were taken, and the OPS and L-cysteic acid content was analyzed by HPLC. The reaction course over time is summarized in Table 5. After a reaction time of 4 h, the L-cysteic acid content in the mixture was 2399.6 mg / L (14.2 mM), which, with a mixture volume of 13.0 ml, corresponded to an absolute molar yield of 0.18 mmol of L-cysteic acid. OPS was completely consumed. Based on the amount of OPS used of 0.18 mmol, this corresponded to a yield of 100%. Tab. 5: Amount of OPS and L-cysteic acid detected by HPLC as a function of reaction time using an OPS-containing fermentation supernatant, Na2SO3, and a CSma-containing cell homogenate from shake flask culture. Example 7: Recombinant production of CSADcc from Cyprinus carpio (carp) in E. coli CSADcc gene: The cDNA sequence of cysteine ​​sulfinic acid decarboxylase (CSAD) from Cyprinus carpio (carp), derived from mRNA, is disclosed in the NCBI database (National Center for Biotechnology Information) under Genbank Sequence ID: AB220585.1 (cds: nt 82–1584). A codon-optimized DNA sequence for expression in E. coli was derived from the corresponding amino acid sequence (publicly available Eurofins Genomics GENEius software) and synthetically produced (Eurofins Genomics). The synthetically produced DNA had the sequence disclosed in SEQ ID NO: 5 and contained the cds of the gene, hereinafter referred to as CSADcc-cds (SEQ ID NO: 5, nt 31 - 1530), encoding a protein having the amino acid sequence disclosed in SEQ ID NO: 6 and referred to as CSADcc.For cloning purposes, the synthetically produced DNA contained an EcoRI cleavage site at the 5' end (SEQ ID NO: 5, nt 25 to 30) and a HindIII cleavage site at the 3' end (SEQ ID NO: 5, nt 1532 to 1537). Vector pCSADcc-pKKj: To produce the vector pCSADcc-pKKj (Fig. 4), which is suitable for recombinant expression of CSADcc-cds, the synthetically produced DNA was cleaved with EcoRI and HindIII and cloned in a known manner as an EcoRI / HindIII fragment into the vector pKKj (see Example 3) cleaved with EcoRI and HindIII. This yielded the vector pCSADcc-pKKj. To express CSADcc-cds in E. coli, the vector pCSADcc-pKKj was transformed into the E. coli K12 JM105 strain in a known manner. Transformed clones were selected on LBamp plates. One clone was selected and cultured in a shake flask. The CSADcc-producing strain was designated E. coli JM105 x pCSADcc-pKKj. CSADcc-cds were expressed in E.E. coli JM105 x pCSADcc-pKKj was cultured in a shake flask analogously to Example 3 for E. coli JM105 x pCSma-pKKj. Shake flask culture: 10 ml of a preculture (OD 1000). 600 3.1 / ml) were used as inoculum for a main culture (1 L Erlenmeyer flask) of 100 ml of SM1 medium supplemented with 15 g / L glucose; 5 g / L peptone; 2.5 g / L yeast extract; 0.005 g / L vitamin B1; 5 mg / L pyridoxal phosphate; and 100 mg / L ampicillin. Growth and induction of the main culture were carried out as described in Example 3. The cells from 100 ml of the shake flask culture (OD 6007.1 / ml) were isolated by centrifugation, and the cell pellet was taken up in 4 ml of KPi7.0 buffer. The cell suspension was used directly for biotransformation experiments. Example 8: Production of Taurine from L-Cysteic Acid by Biotransformation 9 ml of the mixture from Example 5 containing 84.5 mg / L L-cysteic acid (Table 4) were placed in a 100 ml Erlenmeyer flask, and 1 ml of cell suspension of the CSADcc enzyme from Example 7 was added. The mixture volume was 10 ml. The mixture was incubated in a chest shaker (Infors) at 37°C and 140 rpm. After 2 h, 1 ml of the mixture was incubated for 5 min at 80°C, centrifuged, and the supernatant was analyzed by HPLC. The L-cysteic acid used had been completely consumed. The amount of taurine formed was 66.4 mg / L. Example 9: Production of taurine from OPS by biotransformation In a 100 ml Erlenmeyer flask, 9 ml of a shake flask culture of strain E.coli W3110- ^serB (Example 2) containing 94.7 mg / L OPS was added, and 0.5 ml of a 0.2 M solution of Na2SO3 in KPi7.0 buffer, 1 ml of CSma cell homogenate from the shake flask culture (Example 3), and 1 ml of cell suspension of the CSADcc enzyme (Example 7) were added. The mixture volume was 11.5 ml. The mixture was incubated in a chest shaker (Infors) at 30°C and 140 rpm. After 4 h, 1 ml of the mixture was incubated for 5 min at 80°C, centrifuged, and the supernatant analyzed by HPLC. The OPS used was completely consumed. At the same time, 34.4 mg / L L-cysteic acid and 40.4 mg / L taurine were formed.Abbreviations used in the figures: bla: Gene conferring resistance to ampicillin (ß-lactamase) kanR: Gene conferring resistance to kanamycin ORI: Origin of replication pr-1: Binding site 1 for primer pr-2: Binding site 2 for primer FRT1: Recognition sequence 1 for FLP recombinase FRT2: Recognition sequence 2 for FLP recombinase araC: araC gene (repressor gene) P araC: Promoter of the araC gene P araB: Promoter of the araB gene Gam: Lambda phage Gam recombination gene Bet: Lambda phage Bet recombination gene Exo: Lambda phage Exo recombination gene ORI101: Temperature-sensitive origin of replication RepA: Gene for the plasmid replication protein A Ptac: tac promoter EcoRI: Cutting site for the Restriction enzyme EcoRI HindIII: cleavage site for the restriction enzyme HindIII CSma: cds of the cysteate synthase gene from M. acetivora CSADcc: cds of the cysteine ​​sulfinic acid decarboxylase gene from C. carpio.

Claims

Claims 1. A process for the production of L-cysteine ​​acid comprising the reaction of O-phospho-L-serine (OPS) with a salt of sulfurous acid (sulfite) and a cysteate synthase (CS enzyme) belonging to enzyme class EC 2.5.1.76 in a biotransformation.

2. A process according to claim 1, characterized in that the CS enzyme is produced by cultivating a strain of microorganisms of the family Enterobacteriaceae that heterologously expresses the CS enzyme in an enzymatically active form.

3. A process according to one or more of claims 1 or 2, characterized in that the CS enzyme is used in the reaction without a prior renaturation step.

4. A method according to one or more of claims 1 to 3, characterized in that the CS enzyme is produced by cultivating a strain of microorganism Escherichia coli which heterologously expresses the CS enzyme in an enzymatically active form. 5.A method according to one or more of claims 1 to 4, characterized in that the OPS used in the reaction is produced biotechnologically.

6. A method according to one or more of claims 1 to 5, characterized in that the OPS used in the reaction is produced with a strain of microorganisms having suppressed activity of the O-phospho-L-serine phosphatase (SerB enzyme) belonging to enzyme class EC 3.1.3.

3.

7. A process according to one or more of claims 1 to 6, characterized in that the CS enzyme has the amino acid sequence specified in SEQ ID NO: 4 or a homologous amino acid sequence thereto, wherein an amino acid sequence homologous to SEQ ID NO: 4 has a sequence identity of at least 50% to SEQ ID NO: 4 and simultaneously exhibits cysteate synthase enzyme activity.

8. A process according to one or more of claims 1 to 7, characterized in that the molar yield of L-cysteine ​​acid, based on the molar amount of OPS used, is at least 60%.

9. A process for the production of taurine, characterized in that L-cysteine ​​acid is produced and decarboxylated in a process according to one or more of claims 1 to 8.

10. A process according to claim 9, characterized in that the decarboxylation is carried out using a cysteine ​​sulfinate decarboxylase (CSAD enzyme) belonging to the enzyme class EC 4.1.1.

29. 11.A process according to claim 10, characterized in that the amino acid sequence of the CSAD enzyme is SEQ ID NO.

6. A process according to one or more of claims 9 to 11, characterized in that the molar yield of taurine, based on the molar amount of L-cysteine ​​acid used, is at least 60%. A process according to one or more of claims 9 to 12, characterized in that all process steps take place in a single reaction mixture (one-pot process).

14. Use of L-cysteine ​​acid produced by a process according to one or more of claims 1 to 8 for the production of taurine.

Images