200 results about "Feedback inhibition" patented technology

O-acetylserine, L-cysteine and sulphurous compounds derived therefrom may be produced using a bacterium belonging to the genus Escherichia which harbors a mutant feedback-resistant serine acetyltransferases in which the amino acid sequence corresponding to positions from 89 to 96 in a wild-type serine acetyltransferase is replaced with any one of the amino acid sequences shown in SEQ ID NOS: 4 to 9, and feedback inhibition by L-cysteine in the bacterium is desensitized.

The present invention describes the production of L-tyrosine by culturing in a medium an Escherichia bacterium which has L-tyrosine-producing ability and which carries a mutant prephenate dehydrogenase which is desensitized to feedback inhibition by L-tyrosine, producing and accumulating L-tyrosine in the medium or in the bacterial cells, and collecting L-tyrosine from the medium or the bacterial cells.

An L-amino acid is produced by culturing a Methylophilus bacterium which can grow by using methanol as a main carbon source and has L-amino acid-producing ability, for example, a Methylophilus bacterium in which dihydrodipicolinate synthase activity and aspartokinase activity are enhanced by transformation through introduction into cells, of a DNA coding for dihydrodipicolinate synthase that does not suffer feedback inhibition by L-lysine and a DNA coding for aspartokinase that does not suffer feedback inhibition by L-lysine, or a Methylophilus bacterium made to be casamino acid auxotrophic, in a medium containing methanol as a main carbon source, to produce and accumulate an L-amino acid in culture, and collecting the L-amino acid from the culture.

The invention provides a recombinant microorganism for producing cytidine and a method for producing the cytidine from the recombinant microorganism. A degradation and use gene of the cytidine is knocked off, and the gene encodes cytidine ammonialyase, ribonucleotide hydrolase, cytidine/uridine kinase and nucleoside transporter. Meanwhile key enzymes in biological synthesis process of the cytidine are over-expressed, including degrading cytidine triphosphoric acid to cytidine triphosphoric acid pyrophosphorylase of the cytidine monohosphoric acid, and catalyzing the cytidine monohosphoric acid to cytidine monohosphoric acid phosphorylase of the cytidine. In addition, pyrimidine nucleoside process is subjected to genetic engineering reform, and feedback inhibition of the synthesis process is relieved. By using a biological fermentation method, the cytidine yield greater than 20g/L can be achieved for a recombinant strain in a fermentation tank of 5L, industrial on-scale production can be achieved, and meanwhile the recombinant microorganism is low in cytidine production cost, small in pollution, green and environmental-friendly and relatively high in popularization and application value.

The invention relates to a method for improving the yield of arginine by the mutation of Corynebacterium crenatum N-acetyl glutamic acid kinase. L-arginine is one of semi-essential basic amino acids for a human body, and has various particular physiology and pharmacology functions. High-yield arginine mutant strain C. crenatum SYPA5-5 is compounded into the arginine through a circulating way, and N-acetyl glutamic acid kinase (NAGK) is a key enzyme in the compounding way and is subject to the feedback inhibition of the product arginine. By using an overlapping PCR (Polymerase Chain Reaction) technique, a GAT (glycerol phosphate acyl transferase) codon used for coding aspartic acid is used for substituting a GGA (General Gonadotropic activity) codon used for coding glycine at the site 287 in the coding NAGK albumen, and the NAGK which has high activity and arginine with obviously reduced by the feedback inhibition can be obtained after the mutation. An argBSD gene is brought into the Corynebacterium crenatum of the high-yield arginine through pJCl-tac, and the expression volume of the key enzyme is further improved. The final acid yield is increased to 36.3g/L from original 28g/L, and the yield of the L-arginine is increased by 29.7 percent.

The invention discloses a method for preparing glutathione by means of an enzymic method. The method comprises the following steps that 1, Gsh F is utilized for generating glutathione in a reaction kettle; 2, regenerating enzyme is added into the reaction kettle, and ADP and/or AMP generated through a reaction is regenerated to be ATP; 3, the Gsh F and the regenerating enzyme which are fixed are separated in the reaction kettle or a filter device is used for separating dissociative Gsh F and the regenerating enzyme; 4, the product GSH and ATP, ADP and AMP in a reaction solution are separated. According to the preparation method, Gsh F enzyme is used for replacing Gsh I enzyme and Gsh II enzyme, a two-step reaction is changed into the one-step reaction, time is saved, and the feedback inhibition of the GSH for the two-step reaction is lowered; an ATP regenerating system for GSH production is established, the ATP consumption is lowered, and the cost is lowered; impurities such as pigment introduced by ATP regenerated by the yeast are avoided, and purification is easy; the enzyme recycling system is built, and large-scale production can be achieved.

The invention relates to a recombinant DNA (deoxyribonucleic acid), strain and method for producing L-valine by fermentation. The recombinant DNA comprises DNA sequence for coding acetohydroxy acid synthetase free of feedback inhibition of three branched-chain amino acids to acetohydroxy acid synthetase, DNA sequence for coding dihydroxy reduction isomerase, and DNA sequence for coding branched-chain amino acid aminotransferase. The strain is corynebacterium or brevibacterium transformed by introducing the recombinant DNA. The method is implemented by culturing the strain to produce the L-valine. In the invention, the expression L-valine is used for producing the bacterium L-valine biosynthetic gene, so the yield of the L-valine can be greatly increased; and the fermentation model, especially the high-temperature short-time fermentation model, is constructed according to the optimum temperature of the L-valine biosynthetic enzyme, so that the metabolism intensity of the strain is enhanced, the activity of the L-valine biosynthetic enzyme is enhanced, and the yield of the L-valine and the conversion rate of the sugar acid can be further increased.

The invention belongs to the technical field of enzyme engineering, and concretely relates to a pyrimidine nucleoside high-yielding strain and a carbamyl phosphate synthetase adjusting site thereof. The invention provides a pyrimidine nucleoside production Bacillus subtilis mutant strain and a carbamyl phosphate synthetase encoding gene. A key regulation site related to carbamyl phosphate synthetase end product feedback inhibition is defined, and provides reference for breeding of later pyrimidine nucleoside high-yielding strains. The Bacillus subtilis mutant strain allows the output of fermentation process produced nucleoside pyrimidine uridine to reach 14-16g/L, and has substantially improved tolerance to different pyrimidine nucleoside structure analogs.

The invention relates to the technical field of biological engineering, in particular to a strain for producing L-leucine and a method for producing the L-leucine. According to the method, corynebacterium glutamicum is induced by using ultraviolet rays and nitrosoguanidine, then key mutants leuAG561D and ilvBG235S which are beneficial to generation of the L-leucine can be generated, research shows that under mutation conditions of leuAG561D and/or ilvBG235S, feedback inhibition of synthesis routes of the L-leucine can be released, the yield of the L-leucine can be greatly increased, a strain which can generate a great deal of the L-leucine can be obtained, the preservation number of the strain is CGMCC NO.13408, the strain is capable of achieving efficient accumulation of the L-leucine in the fermentation process, and the L-leucine can be up to 4.7g/L.

The invention discloses a trichoderma viride W2 capable of producing a thermophilic ethanol-resistant beta-glucosidase and an application thereof. The trichoderma viride W2 is preserved in the China General Microbiological Culture Collection Center (CGMCC) on August 23, 2010, and the preservation number of the trichoderma viride W2 is CGMCC No.4098. The trichoderma viride W2 can produce a new beta-glucosidase, the enzymatic activity of the new beta-glucosidase reaches 346.7U/mL, the optimal reaction pH value is 4.8, the optimal reaction temperature is 70 DEG C, and the new beta-glucosidase is suitable for pyrohydrolysis and has an obvious glucose feedback inhibition effect. The ethanol the concentration of which is 10% has a maximal effect on promoting the enzymatic activity and improves the enzymatic activity of the beta-glucosidase by 1.6 times, and the resistant ability of the ethanol reaches 30%, so that the cellobiose inhibition can be effectively eliminated, the yield of the ethanol is improved by nearly 3 times, and the terminal product inhibition is effectively eliminated. Thus, the beta-glucosidase can be used for simultaneous saccharification and fermentation of lignocellulose raw materials, has a rare promoting effect in China, effectively increases the yield of the cellulosic ethanol, lowers the production cost, and accelerates the industrialized progress of the cellulosic ethanol.

The invention relates to a method for preparing bio-ethanol by taking seaweed processing waste as raw material, which is characterized by comprising the steps: selecting the seaweed processing waste, and pretreating the raw material by sulfuric acid or hydrogen peroxide; then, adding cellulase or cellobiase for cellulose compound enzymolysis, and filtering enzymolysis liquid to remove insoluble components; and finally, supplementing inorganic salt, inoculating saccharomyces cerevisiae strain, and carrying out alcoholic fermentation under the anaerobic condition. The original structure of algae cellulose is changed by the pretreatment process, and the action probability between the cellulose and degrading enzyme can be promoted, so that the enzymolysis efficiency of the cellulose is improved; furthermore, after the cellulose is treated by the compound enzymolysis of the cellulase and the cellobiase, the feedback inhibition of the cellobiose for the cellulose can be effectively eliminated, the content of glycolysis sugar of yeast can be improved, and the yield of alcoholic fermentation is further improved.

The invention provides a method for producing ethanol by simultaneous high-efficiency saccharification half enzymolysis and fermentation of straw lignocellulose. A pretreated straw lignocellulose raw material is subjected to pre-enzymolysis, and then is added with saccharomyces cerevisiae for simultaneous enzymolysis and fermentation. In the method, the pretreated straw lignocellulose raw material is subjected to the pre-enzymolysis process, most of the cellulose in the raw material (about 80 percent of the total cellulose) is transformed into micromolecular sugar during the process, the raw material is added with a certain amount of yeast for simultaneous enzymolysis and fermentation, the rest cellulose raw material is continuously subjected to the enzymolysis, and glucose in the enzymolysis process is timely transformed into the alcohol simultaneously, so that the feedback inhibition in the enzymolysis process is removed, and the yield of the cellulose-transformed alcohol is improved.

The invention provides a gene engineering bacterial strain for producing L-malic acid as well as a construction method and application thereof. In the invention, key phosphoenolpyruvate carboxykinase(PEPCK) related to the L-malic acid, malate dehydrogenase (MDH) and fumarase (FumC) are transformed to obtain the gene engineering bacterial strain; a deactivation mutation is carried out on the fumCto cause the interruption of a metabolic flux at the converting position from the malic acid to the fumaric acid so as to accumulate the target product L-malic acid; before the mdh, the promoter of aninner source pepck gene is added to generate the metabolic flux biased towards the malic acid; in addition, through the inducement of monofluorine sodium acetate, the activity of the PEPCK is improved, and the product feedback inhibition is greatly reduced. The bacterial strain applied to the fermentative production of the L-malic acid so as to obviously improve the yield of L-malic acid. The invention has advantages of simple technology, obvious effect and low cost and can satisfy the demand of markets.

The invention discloses a variable step size normalized sub-band adaptive filter method applied to acoustic feedback inhibition. According to a hearing-aid feedback control system based on a normalized sub-band adaptive filter algorithm, on the basis of a system noise cancellation principle, estimation is carried out through adoption of an iterative shrinkage method, thereby obtaining noiseless sub-band prior error power; and each sub-band step size is updated, thereby achieving the purpose of eliminating an acoustic feedback signal. According to the method, through adoption of the variable step size adaptive filter method, a coefficient of a sub-band filter is updated; through application of the method in the hearing-aid feedback control system with a long echo path and a short echo path, the acoustic feedback signal can be eliminated well; moreover, relatively high convergence rate and relatively low maladjustment can be obtained; and the contradiction between the steady state maladjustment and the convergence rate in the adaptive filter method is solved.

The invention provides a 5-aminolevulinic acid (ALA) synthetase. The amino acid sequence of the ALA synthetase has mutation at the amino acid residues of the 40th site, the 365th site, the 75th site,the 29th site and the 44th site corresponding to the amino acid sequence as shown in SEQ ID NO:1. The ALA synthetase provided by the invention obviously improves the activity and also partially relieves the feedback inhibition of hemachrome. Furthermore, the invention also provides methods for preparing and modifying the ALA synthetase, an expression vector containing the ALA synthetase, host cells containing the ALA synthetase, and application of the ALA synthetase in ALA production.

The invention belongs to the technical field of lactobacillus cultivation, and relates to a high density fermentation medium for feeding lactobacillus, and a corresponding fermentation method. According to the present invention, a strategy of employing pH feedback to control glucose feeding is adopted, and the density of lactic acid in fermentation broth is reduced, such that feedback inhibition effect of lactic acid is released. With the fermentation medium and the fermentation method provided by the present invention, thalline density of cultivated saliva lactobacillus is substantially improved comparing to that obtained with common fermentation method, live bacteria content is no less than 10<10>cfu/ml, which is increased by 50 times or more than the content of live bacteria cultivatedwith a common MRS medium, such that high density fermentation of saliva lactobacillus is realized. Therefore, separating cost of biomass can be reduced, production period can be shortened, productioncost can be reduced, and production efficiency can be improved.

The invention discloses a fibrous bed reactor and the equipment and process for extracting separation and coupling production of propionic acid. The invention utilizes an immobilized fibrous bed reactor unit, a membrane separation unit, an extraction and anti-extraction unit and an elution and condensation unit to realize the efficient production of propionic acid. The device has strong feasibility, simple operation, easy realization of automation, immobilized materials, long using life of the membrane and the matching equipment, convenient maintenance and good application prospect. Through extracting separation and coupling production technology, the separation of propionic acid is realized. The invention radically eliminates the feedback inhibition of propionic acid, implements the high density fermentation of propionibacterium and greatly improves the production efficiency of propionic acid through the fermentation method. The extracted water phase is returned to the reactor for recycle after elution and condensation by an elution device, which eliminates the harm of extractant for propionibacterium from the root.

The invention relates to an in-vitro directed coevolution method for modifying L-phenylalanine gene engineering strains, which is realized in a way that: using genes aroG and pheA on an L-phenylalanine gene engineering strain constructed in the room as a whole; carrying out the in-vitro directed coevolution modification by using an error-prone PCR technology and a recombinant DNA technology; and screening to obtain a mutant strain, of which the yield of L-phenylalanine is increased by 114%. In the invention, by modifying the gene formed by coupling and connecting aroG and pheA in series, the key genes aroG and pheA in the metaboly process of the L-phenylalanine are used as a whole to carry out the directed modification, thereby obtaining a new metabolic balance, so that the expressed enzyme has high-efficiency catalytic activity and can resist the feedback inhibition of the L-phenylalanine, thereby obtaining the new modified high-yield L-phenylalanine gene engineering strain by screening. The method can provide an example for modifying the acid production rate of any amino acid gene engineering strain.