Engineering bacterium for synthesizing L-serine by utilizing monocarbon compound raw material, construction method and application

Abstract

The invention belongs to the field of bioengineering, and particularly discloses an engineering bacterium for synthesizing L-serine by using a one-carbon compound raw material, a construction method and application. The strain can be used for synthesizing L-serine by taking a monocarbon compound as a raw material. According to the invention, alcohol oxidase and aldolase derived from different microorganisms are creatively subjected to series combination expression, and genetically engineered bacteria capable of utilizing a one-carbon compound raw material are successfully constructed. The strain has unique metabolic capability, can efficiently convert methanol and glycine substrates into L-serine with high added value without the participation of tetrahydrofolate coenzyme, opens up a new path for the production of L-serine, can significantly optimize the production process and reduce the production cost, and has important application value in the field of biological manufacturing.

Description

Technical Field

[0001] The present invention focuses on a method for constructing an engineering bacterium for producing L-serine using a one-carbon compound as a starting material by means of biological transformation and its practical application, and belongs to the field of genetic engineering technology. Background Art

[0002] L-serine is a bio-based chemical with diverse functions and wide applications. It has high market value and broad market prospects in many fields such as pharmaceuticals, cosmetics, food and fine chemicals. It is not only a key precursor for the synthesis of proteins and phospholipids, but also participates in physiological processes such as one-carbon metabolism, neurotransmitter synthesis and immune regulation. Therefore, it has attracted much attention in medicine, nutrition and biomaterials. Traditionally, the production of L-serine mainly relies on chemical synthesis or protein hydrolysis, but these methods usually have problems such as high raw material costs, complex processes and serious environmental pollution, which limit their large-scale application. In recent years, with the rapid development of synthetic biology and metabolic engineering technology, the production of L-serine by microbial fermentation has become a research hotspot. The researchers modified Escherichia coli ( Escherichia coli ) and Corynebacterium glutamicum ( Corynebacterium glutamicum ), optimize sugar metabolism pathways, enhance serine synthesis capacity, reduce by-product accumulation, and use renewable raw materials (such as glucose, xylose, etc.) as carbon sources to successfully construct an efficient L-serine production strain. However, despite certain progress in strain modification and process optimization in recent years, the existing fermentation system still faces many challenges, such as limited precursor supply, unbalanced metabolic flow distribution, product toxicity affecting cell growth, and low substrate utilization efficiency. These factors have resulted in the fermentation yield and rate of L-serine still being unable to meet the needs of industrial production, limiting the further promotion and application of this technology.

[0003] Compared with traditional chemical synthesis, protein hydrolysis and microbial fermentation, bioenzyme catalysis has been widely used in the industrial production of chiral chemicals, especially in the fields of pharmaceutical intermediates and fine chemicals, due to its mild reaction conditions, high stereoselectivity and environmental friendliness. This method relies on efficient enzyme catalysis to reduce the formation of by-products, improve the yield of target products and reduce environmental pollution, and is considered to be a green and sustainable biomanufacturing strategy. At present, the key enzyme involved in the biosynthesis of L-serine is mainly serine hydroxymethyltransferase (SHMT). The reaction catalyzed by this enzyme is relatively complex. It not only requires pyridoxal phosphate (PLP) as a coenzyme, but also relies on tetrahydrofolate (THF) as a one-carbon donor to participate in the reaction to achieve the conversion of glycine to L-serine. The multi-component dependence of this process makes the enzymatic system more complicated, increases the consumption of substrates and cofactors, and thus increases the production cost. In addition, the separation and purification of the product is also affected, which further limits the promotion and application of this method in industrial production. In one of the alternative attempts, Ma Cuiqing's team at Shandong University designed and constructed an efficient in vitro enzyme cascade reaction system to achieve highly selective synthesis of L-serine from glycerol. The enzymes involved include alditol oxidase, D-lactate dehydrogenase, L-alanine dehydrogenase, formate dehydrogenase, and catalase. After optimizing the dosage ratio of each enzyme, the system successfully synthesized 17.58 mM L-serine with 18.51 mM glycerol as substrate, showing a high substrate conversion rate and product yield [Guo S, et al. Enhancedl-Serine Production from Glycerol by Integration with ThermodynamicallyFavorable D-glycerate Oxidation. ACS Sustainable Chemistry&Engineering, 2022,10(8): 2587-2592.]. Therefore, developing a simpler, more efficient and economically feasible method for producing L-serine remains the focus and challenge of current research. Summary of the invention

[0004] The primary purpose of the present invention is to provide a genetically engineered strain and its application, which can efficiently convert and synthesize L-serine using a one-carbon compound as a raw material. Another technical problem to be solved by the present invention is to provide a method for constructing and obtaining the above genetically engineered strain.

[0005] The present invention is achieved through the following technical ideas: using commercial recombinant expression vectors, alcohol oxidase and aldolase from different microbial sources are combined in series, and after induced expression and test screening, a genetically engineered strain with excellent catalytic synthesis ability is obtained.

[0006] The present invention firstly provides an engineering bacterium for synthesizing L-serine using a one-carbon compound raw material. Alcohol oxidase and aldolase are simultaneously introduced into a starting bacterium, and the starting bacterium is Escherichia coli or Corynebacterium glutamicum which can produce L-serine itself.

[0007] Specifically, the alcohol oxidase is derived from Phanerodontia chrysosporium ,or Aspergillus japonicus , or Neurospora tetrasperma ,or Gloeophyllum trabeum ,or Collybiopsis luxurians ,or Ogataea thermomethanolica ; The aldolase is derived from Geobacter sulfurreducens ,or Caulobacter vibrio ,or Aeromonas jandaei ,or Sphaerobacter thermophilus ,or Thermae thermophilic ,or Natranaerobius thermophilus .

[0008] More specifically, the alcohol oxidase is PcAOX, whose GenBank accession number is CDG66232.1, or AjAOX, whose GenBank accession number is RAH81525.1, or NtAOX, whose GenBank accession number is EGO55033.1, or GtAOX, whose GenBank accession number is ABI14440.1, or ClAOX, whose GenBank accession number is KIK62555.1, or OtAOX, whose GenBank accession number is AHC95541.1; The aldolase is GsTA, whose GenBank accession number is AAR36798.1, or CvTA, whose GenBank accession number is AAK25055.1, or AjTA, whose GenBank accession number is BAA20404.1, or StTA, whose GenBank accession number is ACZ39765.1, or TtTA, whose GenBank accession number is AAS80745.1, or NtTA, whose GenBank accession number is ACB84140.1.

[0009] Preferably, the alcohol oxidase is GtAOX, and the aldolase is AjTA; The alcohol oxidase is ClAOX, and the aldolase is GsTA; The alcohol oxidase is OtAOX, and the aldolase is StTA; The alcohol oxidase is NtAOX, and the aldolase is StTA; The alcohol oxidase is OtAOX and the aldolase is CvTA.

[0010] The present invention also provides a method for constructing the engineered bacteria, which comprises introducing a plasmid simultaneously expressing the alcohol oxidase coding gene and the aldolase coding gene into a starting bacterium; or introducing plasmids respectively expressing the alcohol oxidase coding gene and the aldolase coding gene into a starting bacterium.

[0011] Specifically, the alcohol oxidase encoding gene and the aldolase encoding gene are codon optimized according to the introduced starting bacteria; the promoter for initiating gene expression is an inducible T7 strong promoter or a tac strong promoter.

[0012] More specifically, the backbone of the plasmid is a pET21b expression vector or a pXMJ19 expression vector, and the corresponding starting bacteria are Escherichia coli and Corynebacterium glutamicum.

[0013] In a specific embodiment, for a plasmid that simultaneously expresses the alcohol oxidase encoding gene and the aldolase encoding gene, a promoter and the alcohol oxidase encoding gene and the aldolase encoding gene are used for tandem expression, wherein a conserved RBS sequence is included between the two genes.

[0014] The present invention provides the use of the engineered bacteria in the preparation of L-serine. Specifically, the use comprises the following steps: culturing the engineered bacteria to produce L-serine; and separating or purifying the produced L-serine.

[0015] The present invention particularly provides a method for synthesizing L-serine using a one-carbon compound raw material based on whole-cell conversion, characterized in that the whole cell of the engineered bacteria is used as a catalyst, glycine and methanol are used as substrates, and a catalytic reaction is performed to generate L-serine.

[0016] Specifically, in a 100 mL phosphate buffer system, a glycine substrate with a final concentration of 65-75 g / L, a pyridoxal phosphate with a final concentration of 0.10-0.15 g / L, a methanol substrate with a final concentration of 0.8-1.2 mol / L, and 20-40 g / L of the whole-cell catalyst are added, the rotation speed is controlled at 100-200 r / min, the dissolved oxygen is set to not less than 25%, the catalytic reaction pH is 6-8, and the catalytic reaction time is 20-40 h.

[0017] The beneficial effect of the present invention is that it provides a genetically engineered strain for synthesizing L-serine using a one-carbon compound as a raw material, which can efficiently convert methanol and glycine substrates into high-value-added L-serine without the participation of tetrahydrofolate coenzyme, thus opening up a new path for the efficient production of L-serine and having better prospects for industrial application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific examples, but it should not be construed as limiting the present invention. The experimental methods used in the examples are conventional methods well known to those skilled in the art unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0019] Example 1: Construction of plasmid and strain for dual enzyme tandem expression As a key enzyme in the biocatalytic system, alcohol oxidase (AOX) plays a core role in the oxidative metabolism of alcohols. Its catalytic mechanism is based on molecular oxygen as an electron acceptor, which promotes the oxidation reaction of alcohol substrates to generate corresponding aldehydes or ketones, accompanied by the production of hydrogen peroxide. A large number of cutting-edge studies have shown that AOX occupies a key position in the methanol metabolism pathway and is the rate-limiting enzyme in the initial stage of methanol metabolism. It oxidizes methanol to formaldehyde, providing the necessary substrate for a series of subsequent complex metabolic reactions, and plays an indispensable role in maintaining the balance of carbon source metabolism in cells. It is worth noting that AOX from different microbial sources shows significant differences in catalytic activity and substrate specificity. AOX from some methylophilic microorganisms shows extremely high affinity and catalytic efficiency for methanol, and can quickly and efficiently convert methanol into formaldehyde under physiological conditions; while AOX produced by other microorganisms not only has low catalytic activity, but also has extremely strict requirements on substrate structure, and can only show weak catalytic activity for alcohols with specific structures. This difference is mainly due to the different amino acid sequences, spatial structures and microenvironments of the active centers of the enzyme molecules, which in turn affect the binding ability of the enzyme to the substrate and the rate of the catalytic reaction. Threonine aldolase (Ta) is also a very valuable enzyme. It has a unique catalytic ability that can promote the aldehyde condensation reaction between different aldehydes and glycine. With the help of this reaction, a variety of L-serine and its derivatives with specific functions can be successfully synthesized. These L-serine and its derivatives have extensive and important applications in many fields such as medicine, food, and cosmetics. For example, in the medical field, they can be used as key intermediates for drug synthesis, and in the cosmetics industry, they can be used to develop skin care ingredients with special effects.

[0020] In view of the unique catalytic functions of alcohol oxidase AOX and aldolase Ta, we proposed an innovative biochemical synthesis strategy, that is, to achieve the tandem expression of AOX and Tt through genetic engineering, which is expected to construct a new biosynthetic pathway to achieve the goal of efficiently producing L-serine or other related amino acids based on one-carbon compounds such as methanol and glycine. If this idea can be successfully put into practice, it will greatly expand the raw material sources for amino acid biosynthesis, effectively reduce production costs, and significantly reduce the environmental pressure caused by traditional chemical synthesis methods, which is in line with the current concept of green chemistry and sustainable development. However, the key to achieving this strategy lies in the screening and identification of enzyme preparations with excellent catalytic performance. The ideal AOX should have high catalytic activity, good substrate specificity and stable enzymatic properties to ensure that one-carbon compounds such as methanol can be efficiently converted into formaldehyde, providing sufficient and stable substrate supply for subsequent Tt-catalyzed reactions. Therefore, in-depth exploration and testing of alcohol oxidase and aldolase resources from different microbial sources is of great significance for the synthesis of L-serine using one-carbon compound raw materials based on bioenzymatic conversion.

[0021] In this example, we screened gene sequences from different microbial sources based on the database resources of alcohol oxidase AOX and aldolase Ta preserved in the laboratory. By performing phylogenetic analysis on the existing gene sequences of alcohol oxidase AOX and aldolase Ta, combined with gene homology and functional conservation, we selected alcohol oxidase and aldolase gene sequences from representative strains of different evolutionary branches, including but not limited to some microorganisms that can tolerate higher concentrations of one-carbon compounds. In a specific example, we selected alcohol oxidases from 6 representative strains, namely, Phanerodontia chrysosporium DSMZ 1547 [PcAOX, GenBank: CDG66232.1], Aspergillus Japanese CBS 114.51 [AjAOX, GenBank: RAH81525.1], Neurospora tetrasperma FGSC2508 [NtAOX, GenBank:EGO55033.1], Gloeophyllum trabeum ATCC 11539 [GtAOX, GenBank: ABI14440.1], Collybiopsis luxurians FD-317 M1 [ClAOX, GenBank: KIK62555.1], and Ogataea thermomethanolica BCC16875 [OtAOX, GenBank: AHC95541.1]. In another specific embodiment, we also selected aldolases from 6 representative strains, namely Geobacter sulfur-reducingATCC 51573 [GsTA, GenBank: AAR36798.1], Caulobacter vibrioides ATCC 19089 [CvTA, GenBank: AAK25055.1], Aeromonas jandaei DK-39 [AjTA, GenBank:BAA20404.1], Sphaerobacter thermophilus ATCC 49802 [StTA, GenBank: ACZ39765.1], Thermus thermophilus DSM 7039 [TtTA, GenBank: AAS80745.1], Natranaerobius thermophilic DSM 18059 [NtTA, GenBank: ACB84140.1].

[0022] According to the above alcohol oxidase AOX and aldolase Ta encoding gene sequences, after codon optimization by Suzhou Jinweizhi Company, they were obtained by whole gene synthesis technology and cloned into the pET21b expression vector to obtain the corresponding recombinant plasmids, namely: pET21b-PcAOX [PcAOX gene sequence is shown in SEQ ID NO.1], pET21b-AjAOX [AjAOX gene sequence is shown in SEQ ID NO.2], pET21b-NtAOX [NtAOX gene sequence is shown in SEQ ID NO.3], pET21b-GtAOX [GtAOX gene sequence is shown in SEQ ID NO.4], pET21b-ClAOX [ClAOX gene sequence is shown in SEQ ID NO.5], pET21b-OtAOX [OtAOX gene sequence is shown in SEQ ID NO.6], pET21b-GsTA [GsTA gene sequence is shown in SEQ ID NO.7], pET21b-CvTA [The CvTA gene sequence is shown in SEQ ID NO.8], pET21b-AjTA [The AjTA gene sequence is shown in SEQ ID NO.9], pET21b-StTA [The StTA gene sequence is shown in SEQ ID NO.10], pET21b-TtTA [The TtTA gene sequence is shown in SEQ ID NO.11], pET21b-NtTA [The NtTA gene sequence is shown in SEQID NO.12].

[0023] A single-plasmid dual-enzyme co-expression system is provided in this embodiment, that is, the alcohol oxidase AOX encoding gene and the aldolase Ta encoding gene are simultaneously expressed in one plasmid. In one embodiment, the dual-enzyme co-expression vector adopts a single promoter mode to express a promoter and the alcohol oxidase AOX encoding gene and the aldolase Ta encoding gene in series, and the two encoding genes can be connected in series in any order. The present invention further provides a recombinant expression vector for dual-enzyme co-expression, preferably a prokaryotic expression vector, including but not limited to pET21b and pXMJ19. In a specific embodiment, the alcohol oxidase AOX encoding gene and the aldolase Ta encoding gene are connected in series using an inducible T7 strong promoter or a tac strong promoter, wherein the alcohol oxidase AOX encoding gene and the aldolase Ta encoding gene are separated by a conservative RBS sequence. The promoter and RBS related sequences used for the co-expression system construction of the present invention are respectively: By commercial one-step efficient seamless cloning (ClonExpress®II One Step Cloning Kit, VazymeBiotech, China) and other molecular assembly technologies, the gene sequences encoding the six representative alcohol oxidases AOX and six representative aldolases Ta selected in this example were randomly concatenated and subcloned into the pET21b or pXMJ19 backbone, and a total of 36 combined co-expression patterns were obtained, namely AjAOX-GsTA, AjAOX-CvTA, AjAOX-AjTA, AjAOX-StTA, AjAOX-TtTA, AjAOX-NtTA, NtAOX-GsTA, NtAOX-CvTA, NtAOX-AjTA, NtAOX-St TA, NtAOX-TtTA, NtAOX-NtTA, GtAOX-GsTA, GtAOX-CvTA, GtAOX-AjTA, GtAOX-StTA, GtAOX-TtTA, GtAOX-NtTA, ClAOX-GsTA, ClAOX-CvT A, ClAOX-AjTA, ClAOX-StTA, ClAOX-TtTA, ClAOX-NtTA, OtAOX-GsTA, OtAOX-CvTA, OtAOX-AjTA, OtAOX-StTA, OtAOX-TtTA, and OtAOX-NtTA.

[0024] In this specific embodiment, the selected inducible expression vector is pET21b, which contains T7 strong promoter related sequences (including operator sequence lacO and conservative RBS sequence). When IPTG or lactose and other inducers are added, the repressor protein will be prompted to leave the operator sequence and start gene expression. In another specific embodiment, the inducible expression vector selected by the present invention is pXMJ19, which contains strong promoter tac related sequences (including operator sequence lacO and conservative RBS sequence), can be replicated in Escherichia coli and Corynebacterium glutamicum, and when IPTG or lactose and other inducers are added, the repressor protein will be prompted to leave the operator sequence and start gene expression.

[0025] Example 2: Preparation of whole-cell catalytic bacterial sludge by high-density fermentation The pET21b recombinant vectors containing different alcohol oxidase encoding genes and aldolase encoding genes in tandem co-expression mode in the above examples were transformed into Escherichia coli BL21 (DE3) to obtain corresponding genetically engineered strains.

[0026] The pXMJ19 recombinant vectors containing different alcohol oxidase encoding genes and aldolase encoding genes in tandem co-expression mode in the above examples were used to transform Corynebacterium glutamicum ATCC 13032 to obtain the corresponding genetically engineered strains.

[0027] In order to achieve efficient synthesis of L-serine based on biotransformation, the present embodiment provides a high-density fermentation culture and bacterial sludge preparation method of a co-expression recombinant strain. The specific steps are: first, the co-expression Escherichia coli recombinant strain obtained in Example 1 is inoculated into a seed culture medium containing ampicillin resistance, or the co-expression Corynebacterium glutamicum recombinant strain obtained is inoculated into a seed culture medium containing chloramphenicol resistance, and shake culture is carried out at 32°C and 200 r / min under shaking conditions for 16-20 hours to obtain a seed culture solution. Then, the seed culture solution is inoculated into a fermentation tank containing 3 L of fermentation medium at an inoculation rate of 5-10%, the culture temperature is set to 32°C, the stirring speed is set to 300-500 r / min, and the culture pH is kept neutral. During the culture process, when the dissolved oxygen level drops below 30%, the speed and dissolved oxygen coupling control system is enabled to automatically adjust the stirring speed to ensure sufficient dissolved oxygen supply. When the bacterial concentration (OD 600 ) When the concentration reaches about 20-40, add IPTG inducer with a final concentration of 0.4-0.6 mM to activate the expression of the target protein, and adjust the culture temperature to below 25°C, continue to maintain the pH value neutral, and induce the culture for more than 20 hours. Finally, use 8000×g centrifugation for 10 minutes to collect the bacteria, and remove the supernatant of the fermentation broth to obtain the recombinant strain sludge, which can be stored in a 4°C refrigerator for later use.

[0028] It should be understood by those skilled in the art that the antibiotics added to the seed culture medium and the fermentation culture medium are used as screening markers for the fermentation culture of the co-expression recombinant strain. The concentration of the antibiotics is not particularly limited, and the working concentration is 30 μg / L. In this embodiment, the components of the seed culture medium are: 2.5 g / L yeast powder, 5 g / L peptone, 5 g / L NaCl, and 37 g / L brain heart infusion; the components of the fermentation culture medium are: 100 g / L glucose, 20 g / L corn steep liquor, 20 g / L molasses, 10 g / L ammonium sulfate, 1 g / L magnesium sulfate, 0.5 g / L potassium dihydrogen phosphate, 0.5 g / L potassium dihydrogen phosphate, 1 g / L sodium citrate, 5 g / L calcium carbonate, 0.1 mg / L biotin, and the culture medium is adjusted to pH 7.0. In this embodiment, the pH of the culture medium is adjusted by 50% acetic acid as the acid solution and 50% ammonia water as the alkaline solution.

[0029] Example 3: Establishment of a whole-cell transformation process for preparing L-serine This embodiment is used to provide a method for synthesizing L-serine using a one-carbon compound raw material based on whole-cell conversion. In one specific embodiment, a biological preparation process for L-serine is established based on the co-expression recombinant Corynebacterium glutamicum constructed in the above Example 2 as a whole-cell catalyst. The production method of L-serine is specifically to add a glycine substrate with a final concentration of 60g / L, a pyridoxal phosphate with a final concentration of 0.15 g / L, a methanol substrate with a final concentration of 0.8-1.0mol / L, 30 g / L of the whole-cell bacterial mud prepared in the above Example 3, control the speed to 200r / min, set the dissolved oxygen to not less than 25%, the catalytic reaction pH to 7.0, the catalytic reaction time to 30 h, and after the reaction is completed, the components of the catalytic reaction liquid are quantitatively analyzed by liquid chromatography (HPLC).

[0030] The results show that the alcohol oxidase encoding gene and the aldolase encoding gene from different microbial sources are co-expressed in series, and the contribution to the synthesis of L-serine by the catalytic strain is quite different. The recombinant Corynebacterium glutamicum strain containing the 30 dual enzyme combination co-expression patterns described in Examples 1 and 2 above catalyzes the reaction of methanol and glycine to produce L-serine, as shown in Table 1. In particular, the alcohol oxidase and aldolase combinations NtAOX-StTA, GtAOX-AjTA, ClAOX-GsTA, OtAOX-StTA and OtAOX-CvTA are simultaneously introduced into Corynebacterium glutamicum, and the best L-serine production effect can be obtained, which provides a feasible path for the green production based on one-carbon compound raw materials in the future.

[0031] Table 1. Analysis of production performance of L-serine prepared by whole cell transformation

[0032] The above contents are only preferred embodiments of the present invention, which are intended to illustrate the technical solutions of the present invention, rather than to limit the protection scope of the present invention. Without departing from the core technical concept of the present invention, those skilled in the art may, based on the specification and claims of the present invention, make appropriate adjustments, changes or equivalent substitutions thereto, and all technical improvements, equivalent solutions and variations within the scope defined by the claims of the present invention shall be deemed to be the protection scope of the present invention. In addition, technical contents not specifically described in the present invention, if they belong to conventional technical means of those skilled in the art, shall also be deemed to be part of the present invention.

Claims

1. An engineered bacterium for synthesizing L-serine using a one-carbon compound raw material, characterized in that: Simultaneously introducing alcohol oxidase and aldolase into a starting bacterium, wherein the starting bacterium is Escherichia coli or Corynebacterium glutamicum; The alcohol oxidase is PcAOX, whose GenBank accession number is CDG66232.1, or AjAOX, whose GenBank accession number is RAH81525.1, or NtAOX, whose GenBank accession number is EGO55033.1, or GtAOX, whose GenBank accession number is ABI14440.1, or ClAOX, whose GenBank accession number is KIK62555.1, or OtAOX, whose GenBank accession number is AHC95541.1; The aldolase is GsTA, whose GenBank accession number is AAR36798.1, or CvTA, whose GenBank accession number is AAK25055.1, or AjTA, whose GenBank accession number is BAA20404.1, or StTA, whose GenBank accession number is ACZ39765.1, or TtTA, whose GenBank accession number is AAS80745.1, or NtTA, whose GenBank accession number is ACB84140.

1.

2. The engineered bacteria according to claim 1, characterized in that The alcohol oxidase is GtAOX, and the aldolase is AjTA; The alcohol oxidase is ClAOX, and the aldolase is GsTA; The alcohol oxidase is OtAOX, and the aldolase is StTA; The alcohol oxidase is NtAOX, and the aldolase is StTA; The alcohol oxidase is OtAOX and the aldolase is CvTA.

3. The method for constructing an engineered bacterium according to claim 1 or 2, characterized in that: A plasmid simultaneously expressing the alcohol oxidase coding gene and the aldolase coding gene is introduced into the starting bacteria; or plasmids expressing the alcohol oxidase coding gene and the aldolase coding gene are separately introduced into the starting bacteria.

4. The method according to claim 3, characterized in that The alcohol oxidase coding gene and the aldolase coding gene are codon optimized according to the introduced starting bacteria; the promoter for starting gene expression is an inducible T7 strong promoter or a tac strong promoter.

5. The method according to claim 4, characterized in that The backbone of the plasmid is a pET21b expression vector or a pXMJ19 expression vector, and the corresponding starting bacteria are Escherichia coli and Corynebacterium glutamicum.

6. The method according to claim 4, characterized in that For a plasmid for simultaneously expressing the alcohol oxidase encoding gene and the aldolase encoding gene, a promoter and the alcohol oxidase encoding gene and the aldolase encoding gene are used for tandem expression, wherein a conserved RBS sequence is included between the two genes.

7. Use of the engineered bacteria as claimed in claim 1 or 2 in the preparation of L-serine.

8. The use according to claim 7, characterized in that The method comprises the following steps: culturing the engineering bacteria to produce L-serine; and separating or purifying the produced L-serine.

9. A method for synthesizing L-serine using a one-carbon compound raw material based on whole-cell conversion, characterized in that: The whole cell of the engineered bacteria as claimed in claim 1 or 2 is used as a catalyst, and glycine and methanol are used as substrates to catalyze the reaction to produce L-serine.

10. The method according to claim 9, characterized in that In a 100 mL phosphate buffer system, add a glycine substrate with a final concentration of 65-75 g / L, a pyridoxal phosphate with a final concentration of 0.10-0.15 g / L, a methanol substrate with a final concentration of 0.8-1.2 mol / L, and 20-40 g / L of the whole-cell catalyst, control the speed to 100-200 r / min, set the dissolved oxygen to not less than 25%, the catalytic reaction pH to 6-8, and the catalytic reaction time to 20-40 h.

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