1763 results about "Oxidative enzyme" patented technology

The invention discloses a xanthine oxidase inhibitory peptide with a kidney improving function and application thereof, and belongs to the technical field of biological medicines.The xanthine oxidase inhibitory peptide is screened out by conducting enzymolysis, separation and purification on litopenaeus vannamei processing by-products and utilizing a molecular docking technology, the amino acid sequence of the xanthine oxidase inhibitory peptide is Pro-Leu-Gly-Pro-Pro-Pro, and the amino acid sequence of the xanthine oxidase inhibitory peptide is Pro-Leu-Gly-Pro-Pro-Pro. And the half inhibition concentration of the polypeptide is 2.356 + / -0.2448 mM. The xanthine oxidase inhibitory peptide is proved to have an improvement effect on hyperuricemia mice, the improvement effect is mainly characterized by reducing the content of serum uric acid, creatinine and urea nitrogen of the hyperuricemia mice, inhibiting the activity of xanthine oxidase (XOD) in serum and livers of the mice, inhibiting synthesis of uric acid and improving kidney injury of the mice, and Toxinpred prediction shows that the xanthine oxidase inhibitory peptide has the effect of inhibiting the activity of xanthine oxidase (XOD) in the serum and livers of the mice. The xanthine oxidase inhibitory peptide is free of toxic and side effects, so that the xanthine oxidase inhibitory peptide has a wide application prospect in preparation of food or drugs for improving renal functions.

The invention discloses a xanthine oxidase inhibitory peptide with uric acid reducing activity and application thereof, and belongs to the technical field of biological medicines.The xanthine oxidase inhibitory peptide is obtained by conducting enzymolysis, separation and purification on processing byproducts such as litopenaeus vannamei heads and shells with xanthine oxidase inhibitory activity. The xanthine oxidase inhibitory peptide is screened by using a molecular docking technology, and the amino acid sequence of the xanthine oxidase inhibitory peptide is Pro-Pro-Val-Pro-Pro-Pro. The xanthine oxidase inhibitory peptide has an XOD (X-Oxidase) half inhibitory concentration of 3.181 + / -0.1786 mM. The invention further proves that the xanthine oxidase inhibitory peptide has a certain improvement effect on hyperuricemia mice, and the xanthine oxidase inhibitory peptide mainly has the effects of reducing the content of serum uric acid, creatinine and urea nitrogen of the hyperuricemia mice, inhibiting the activity of xanthine oxidase (XOD) in serum and liver of the mice, inhibiting synthesis of uric acid and improving kidney injury of the mice, and the xanthine oxidase inhibitory peptide has a certain improvement effect on the hyperuricemia mice through Toxinpred prediction. The xanthine oxidase inhibitory peptide uric acid reducing peptide is free of toxic and side effects and has a wide market application prospect.

The invention discloses a colorimetric and fluorescent dual-mode nano-enzyme sensor. The colorimetric and fluorescent dual-mode nano-enzyme sensor comprises nano-enzyme, hydrogen peroxide and a colorimetric probe, wherein the nano-enzyme is prepared from ZrCl4, 2-aminobiphenyl dicarboxylic acid and Cu (NO3) 2 by a one-pot method; the colorimetric probe is TMB, can oxidize colorless TMB into blue oxTMB, generates an ultraviolet absorption peak at 652 nm, and has a strong fluorescence emission peak at 405 + / -5 nm. The zirconium-based metal organic framework UiO-67-NH2 with high stability is used as a carrier, Zr < 4 + > sites are replaced by part of Cu < 2 + >, the fluorescent nano-enzyme with peroxidase activity is formed, and the problems that free enzyme is difficult to recover, the stability is low and the like are solved.

Pharmaceutical compositions for the transmucosal delivery of N-N-dimethyltryptamine (DMT) acceptable salt or prodrug thereof in combination with a monoamine oxidase inhibitor to achieve desired bioavailability suitable for the treatment of neurological disorders.

The invention relates to the technical field of enzyme engineering, in particular to an L-glutamate oxidase mutant as well as preparation and application thereof. Through mutation of the 77th amino acid and the 171st amino acid, the active center configuration of the enzyme is optimized, the binding capacity with a substrate and the catalytic conversion efficiency are enhanced, and the enzyme activity is remarkably improved. The mutant disclosed by the invention shows stronger specificity to L-glutamic acid (salt), effectively reduces non-specific reaction and improves the product purity. And in the presence of a high-concentration substrate, the enzyme activity is not inhibited by the substrate. The prepared L-glutamate oxidase mutant with high enzymatic activity can be efficiently expressed in escherichia coli, the problem that the expression quantity of natural enzymes in streptomyces is limited is solved, the acquisition efficiency of the enzymes is greatly improved, and the production cost is reduced. The mutants can be directly applied to biological manufacturing of alpha-ketoglutaric acid, so that the production efficiency of products is remarkably improved.

The invention belongs to the field of bioengineering, and particularly discloses a glutamate oxidase mutant with improved enzymatic activity. According to the invention, site-specific mutagenesis and saturation mutation are carried out on glutamate oxidase coding genes derived from streptomyces mobaraensis, wherein mutations are C536R, P532R, Q378D, V548E and G236D. After the mutant obtained by the invention is induced and purified, the specific enzyme activity of the optimal glutamate oxidase mutant is 1.69 U / mg and is improved by about 30% compared with that of wild bacteria, which shows that the 378-site amino acid residue has great influence on the catalytic action and stability of the enzyme. In addition, the invention also discloses a construction method of the glutamate oxidase mutant with improved enzymatic activity and application of the glutamate oxidase mutant in production of amino acid derivatives such as alpha-ketoglutaric acid. Therefore, the beneficial mutant provided by the invention can lay a good foundation for industrial fermentation production of alpha-ketoglutaric acid and other products.

The invention discloses a tumor cholesterol metabolism regulation microneedle patch and a preparation method, the microneedle patch comprises a needle tip and a backing which are connected, the needle tip comprises a needle tip body and nanoparticles loaded on the needle tip body, the nanoparticle is a manganese ion-doped organic metal framework, the outer layer of the manganese ion-doped organic metal framework is modified with a targeting agent, cholesterol oxidase and superoxide dismutase are carried on the manganese ion-doped organic metal framework, the targeting agent can target a CD44 receptor, and the organic metal framework can carry drugs. The targeted drug can enter tumor cells in a targeted mode, superoxide dismutase catalyzes superoxide anions overexpressed in the tumor cells to generate H2O2 and O2, O2 needed by catalysis is provided for cholesterol oxidase, cholesterol at the tumor site is consumed by the cholesterol oxidase, accumulation of 7-DHC is reduced, meanwhile H2O2 can be generated, and the cholesterol oxidase can be used for catalyzing the tumor site. H2O2 is catalyzed by manganese ions through a Fenton-like reaction to generate OH to induce tumor cells to generate ferroptosis, so that ferroptosis-immune synergistic treatment is realized.

The invention belongs to the technical field of creatine kinase detection kits, and particularly relates to a creatine kinase detection reagent, a creatine kinase detection kit and application, the creatine kinase detection reagent comprises a buffer solution, creatine phosphate, glycerol, glycerol kinase, glycerophosphate oxidase, peroxidase and a color developing agent, and further comprises a CK activation reducing agent and perfluoro and polyfluoroalkyl substances, the CK activation reducing agent is a sulfur-containing reducing agent. According to the method, the detection accuracy can be improved.

The invention belongs to the technical field of medicines, and particularly relates to application of eupatorium chinense extract in preparation of a medicine for treating gout. Researches show that the eupatorium chinense extract and the active components thereof have good biological activity and can inhibit the activity of xanthine oxidase (XOD). Molecular docking experiments also show that the eupatorium chinense extract and xanthine oxidase have good binding energy. Further research finds that the eupatorium chinense extract can reduce the levels of uric acid and creatinine in serum in a hyperuricemia mouse body, and has good uric acid reducing activity. In the field of treatment of hyperuricemia and gout, many traditional medicines have many adverse reactions. Compared with the prior art, the eupatorium chinense serving as a traditional Chinese medicine provides a safe and effective natural medicine for treating hyperuricemia and gout or gout complications due to the efficient uric acid reducing effect of the eupatorium chinense.

The invention discloses a fungus extract capable of effectively regulating uric acid metabolism and relieving inflammation as well as a preparation method and application of the fungus extract, and belongs to the technical field of deep processing of edible fungi. Schizophyllumcommuneh and poplar phellinus sporocarp are mixed and extracted, and the prepared fungus extract can effectively inhibit activity of xanthine oxidase in serum and liver of mice, reduce content of uric acid, creatinine, urea nitrogen and the like in serum and promote excretion of uric acid, creatinine, urea nitrogen and the like in urine; meanwhile, the content of inflammatory markers such as IL-6 and TNF-alpha in mouse serum can be effectively reduced, inflammatory infiltration of liver and kidney cells is relieved, and the problem that an existing edible mushroom extract is not ideal in treatment effect on hyperuricemia is solved.

The invention relates to the field of preparation and application of biological peptides, in particular to a swelling hippocampal peptide and application thereof in preparation of uric acid reducing and gout resisting products. The amino acid sequence is shown as SEQ ID NO.1. The uric acid reducing effect of the compound is proved through in-vitro xanthine oxidase (XOD) and adenosine deaminase (ADA) inhibition experiments and cell experiments; on the basis, the uric acid reducing and gout resisting activity of the peptide sequence is further verified by means of a hyperuricemia animal model. The achievement provides a solid theoretical support for high-value development and utilization of the hippocampus japonicus and research and development of uric acid reducing and gout resisting related products.

The invention relates to an application of sea cucumber intestine polysaccharide in preparation of uric acid lowering drugs. The preparation method of the sea cucumber intestine polysaccharide comprises the following steps: performing enzymolysis treatment on sea cucumber intestines by using papain, performing enzyme deactivation, performing centrifugation, and taking supernate; and carrying out graded alcohol precipitation on the supernate, centrifuging, taking precipitate, deproteinizing and freeze-drying. The preparation method is simple, green and environment-friendly. The sea cucumber intestine polysaccharide prepared by the method can effectively inhibit the activity of xanthine oxidase; the sea cucumber intestine polysaccharide has no toxic effect on HK-2 cells. The compound has a uric acid reducing effect on HK-2 hyperuricemia cells.

The invention belongs to the technical field of biomedical materials, and discloses injectable heterogeneous cascade nano-enzyme antibacterial hydrogel as well as a preparation method and application thereof. The preparation method comprises the following steps: in a process of preparing cerium dioxide nano-enzyme by a reverse micelle method, introducing molybdenum disulfide nano-particles with a nano flower-shaped structure so as to deposit the cerium dioxide nano-enzyme on the surfaces of the molybdenum disulfide nano-particles in situ to obtain nano-composite particles; through electrostatic interaction, glucose oxidase is loaded on the surfaces of the nano composite particles to form a heterogeneous cascade nano enzyme material; the preparation method comprises the following steps: uniformly mixing sodium alginate and hyaluronic acid in water, and sequentially adding an NO donor, a heterogeneous cascade nano-enzyme material and a cross-linking agent to obtain the injectable heterogeneous cascade nano-enzyme antibacterial hydrogel. The preparation method is simple, and the injectable heterogeneous cascade nano-enzyme antibacterial hydrogel has a strong antibacterial effect and can be used for preparing the antibacterial hydrogel. Particularly, the compound has a remarkable killing effect on gram-negative bacteria and gram-positive bacteria.

According to the method, phosphomolybdic acid, copper chloride and ferric chloride serve as precursors, copper and iron-containing phosphomolybdic acid nano-enzyme (Cu, Fe-PMs) with peroxidase-like activity is synthesized through a microwave method, under the acidic condition, on one hand, the surface of Cu and Fe-PMs carries negative charges, high affinity is generated between Cu and Fe-PMs and a substrate TMB with positive charges, and on the other hand, the surface of Cu and Fe-PMs has negative charges; on the other hand, Cu / Fe / Mo three-metal redox couple accelerates the regeneration of Fe < 2 + > and plays an important role in the activity of peroxidase, and meanwhile, due to the introduction of sodium dehydroacetate, Cu and Fe in Cu and Fe-PMs and pyranoid ring and keto O in sodium dehydroacetate interact through coordinate bonds to cause electron interaction, so that the peroxidase-like activity of Cu and Fe-PMs is enhanced, and the peroxidase-like activity of Cu and Fe-PMs is improved. And the Fenton reaction is enhanced through transfer of electrons among the sodium dehydroacetate, the Cu and the Fe-PMs. When Cu and Fe-PMs oxidize TMB and H2O2, sodium dehydroacetate enhances the absorbance of the system, and on the basis, a novel colorimetric rapid detection method of sodium dehydroacetate is established.

The invention discloses an inositol oxidase mutant and application thereof, and belongs to the technical field of gene engineering. The inositol oxidase mutant is obtained by mutating 113th amino acid of an amino acid sequence shown as SEQ ID NO.1, and the mutation is that the 113th amino acid is mutated from T to A. The enzyme activity of the inositol oxidase mutant is remarkably improved, the thermal stability is good, the half-life period is long, and the yield and conversion rate of glucuronic acid can be improved.

The invention discloses camel milk polypeptide with xanthine oxidase inhibitory activity and application thereof.The camel milk polypeptide is prepared by taking fresh camel milk as a raw material, conducting low-temperature centrifugation to remove fat, conducting triple enzymolysis through papain, pepsin and trypsin to obtain enzymatic hydrolysate, enabling the enzymatic hydrolysate to pass through an ultrafiltration membrane (the molecular weight cutoff is 10 kDa) to obtain filtrate, and conducting freeze-drying to obtain the camel milk polypeptide. The compound has xanthine oxidase inhibitory activity. The invention also discloses a small molecule polypeptide with xanthine oxidase inhibitory activity. The filtered solution is screened and combined with polypeptides by adopting a xanthine oxidase affinity ultrafiltration method, the activity of the polypeptides is verified through molecular docking and in-vitro enzyme inhibition, four small-molecule polypeptides with xanthine oxidase inhibitory activity are obtained, the sequence of the small-molecule polypeptides is shown as any one of SEQ ID NO.1-4, and the small-molecule polypeptides can be used for preparing drugs with the effect of inhibiting the uric acid level.

The invention relates to a preparation method and application of a carbon dot-based nano enzyme. The preparation method of the carbon dot-based nano-enzyme comprises the following steps: taking sucralose and B vitamins as raw materials, and preparing the carbon dot-based nano-enzyme through a one-pot hydrothermal method. The preparation method of the carbon dot-based nano-enzyme provided by the invention is simpler in catalytic condition and higher in safety. The carbon dot-based nano-enzyme prepared by the invention has the advantages of high oxidase-like activity, low drug resistance, high biocompatibility and the like, can inhibit multi-drug-resistant bacteria, and can be applied to the aspects of aquatic product preservation and the like.

The invention belongs to the technical field of biology, and particularly relates to a method for producing xylitol through two-step enzyme catalysis of hemicellulose hydrolysate, and the method comprises the following steps: taking hemicellulose hydrolysate as a raw material, adding arabinose dehydrogenase, NADH oxidase and coenzyme NADH, and carrying out first-step fermentation until no L-arabinose residue exists in fermentation liquor to obtain fermentation reaction liquor I; and adding xylose reductase and glucose dehydrogenase into the fermentation reaction liquid I, and carrying out second-step fermentation to obtain a fermentation product containing xylitol. According to the two-step enzyme catalysis method provided by the invention, xylitol is prepared, and high-purity xylose does not need to be used as a raw material; according to the present invention, the cheap hemicellulose hydrolysate can be directly adopted as the raw material, the xylose conversion rate and the xylitol yield can exceed 99%, the impurity arabitol content in the product is low, the other impurity saccharic acid is easy to separate, and the problems of complex process, large separation difficulty and high cost in the xylitol refining process are successfully solved.

The present invention provides a manganese metal-organic framework material with oxidase properties, a preparation method, and an application thereof. The material is prepared by the following method: using 1,3,5-trimethic acid as an organic ligand, manganese acetate tetrahydrate as a manganese source, and a water-ethanol solution as a solvent, to obtain a manganese metal organic framework (MOF) precursor via a solvothermal synthesis technique; the manganese MOF precursor is post-synthetically modified using an oxidant, wherein the oxidant is a mixed solution of an aqueous alkali metal hydroxide solution and H2O2, and the ratio of the manganese MOF precursor to the alkali metal hydroxide is (400-600) mg:(0.5-2) mmol. By using specific types and amounts of manganese MOF precursors and oxidants, the resulting metal-organic framework nanomaterial has specific enzyme-like properties, can exert the function of uricase, and has optimal and high uricase activity under neutral pH conditions.

The invention discloses a genetically engineered bacterium for producing glucuronic acid as well as a construction method and application of the genetically engineered bacterium, and belongs to the technical field of genetic engineering. According to the genetically engineered bacterium for producing glucuronic acid, an inositol oxidase gene MMIOX is integrated on a site of a uronic acid isomerase gene uxaC. According to the invention, an inositol oxidase gene MMIOX is integrated on a genome of a genetically engineered bacterium for producing glucuronic acid, and a uronic acid isomerase gene uxaC is knocked out at the same time, so that the genetically engineered bacterium can efficiently catalyze inositol reaction to generate glucuronic acid through the integrated inositol oxidase gene MMIOX; the glucuronic acid isomerase gene uxaC is knocked out, so that isomerization reaction of glucuronic acid can be avoided, and the yield of glucuronic acid is further increased.

The invention discloses a Vinck Cellulomicrobe and application thereof in degradation of corn straw and improvement of soil fertility, and belongs to the field of agricultural microbial technology and solid waste resource utilization. The bacterial strain can secrete a plurality of hydrolase and oxidase including AA10 family lytic polysaccharide monooxygenase, AA2 peroxidase, GH3 and GH1 beta-glucosidase, GH16 / GH17 beta-glucosan endonuclease and AA1 multi-copper oxidase. The bacterial strain has the advantages that the bacterial strain can secrete a plurality of hydrolase and oxidase; fermentation liquor is applied to soil according to the straw mass ratio of 1: 5, and the corn straw degradation rate can be increased under the condition that the mass ratio of soil to straw is 100: 1. Meanwhile, the microbial agent can synergistically improve soil nutrients and increase the contents of rapidly available phosphorus, rapidly available potassium, alkali-hydrolyzable nitrogen, soluble organic carbon and total phosphorus in soil. According to the microbial agent, a straw lignocellulose structure is effectively cracked through a multi-enzyme system synergistic effect, and the dual effects of accelerating straw degradation and improving soil fertility are achieved.

The invention relates to euphausia superba peptide with uric acid reducing activity and application thereof. The euphausia superba peptide is a short peptide obtained by extraction, enzymolysis, separation and purification from degreased euphausia superba powder, and the amino acid sequence of the euphausia superba peptide is Ser-Ala-Gly-Lys-Thr. Researches show that the peptide can reduce the generation of uric acid by inhibiting the activity of xanthine oxidase and promote the excretion of uric acid. In-vitro cell experiments prove that under the concentration of 10 mu M, the inhibition rate of the peptide on xanthine oxidase reaches 23.1%; animal experiments show that the blood uric acid level of mice in a high-dose group (50mg / kg) is reduced by about 40% compared with that in a model group. The invention also develops a health-care beverage and a medicinal preparation which take the peptide as an active component, and provides a new choice for preventing and treating hyperuricemia and gout.

The invention belongs to the technical field of catalytic materials, and particularly relates to high-entropy alloy nanoparticles used as a biocatalyst and application of the high-entropy alloy nanoparticles. The PtFeCuCoNi high-entropy alloy nano-particles with pH adaptability are developed through a one-step solvothermal synthesis method, it is found that the PtFeCuCoNi high-entropy alloy nano-particles can serve as potent oxidase, can generate reactive oxygen species (ROS) and effectively kill bacteria such as MRSA under the acidic condition, and can play the functions of superoxide dismutase and catalase under the neutral condition, so that the PtFeCuCoNi high-entropy alloy nano-particles with the pH adaptability can be used for effectively killing bacteria such as MRSA. Active oxygen in cells is efficiently removed, oxidative stress is relieved, and the cell protection effect is achieved.

The invention discloses a manganese / cobalt-based MOFs nano-enzyme with a hollow structure as well as a preparation method and application thereof, and belongs to the technical field of preparation and application of novel nano-materials. According to the invention, ZIF-67 is used as a carrier, potassium permanganate is used as a manganese source, and the Mn / Co-MOF nano-enzyme with a hollow structure and highly dispersed manganese species is prepared through a loading-low temperature pyrolysis strategy. The antioxidant substances in the black tea can inhibit the oxidase-like activity of the hollow-structure manganese / cobalt-based MOFs nano-enzyme, so that the color of the system is changed, and based on the principle, the method for detecting the total oxidation resistance of the tea based on the hollow-structure manganese / cobalt-based MOFs nano-enzyme is established. Meanwhile, the method is used for monitoring the change of the total antioxidant capacity in the black tea fermentation process, a new method for judging the fermentation degree of the black tea is established in combination with data processing methods such as machine learning, and a new means is provided for improving the quality of the black tea and intelligently processing tea leaves.

The invention relates to the field of biological functional materials, and discloses a preparation method and application of a Cu-doped W18O49 nano-enzyme with near-infrared two-region photoresponse. The specific method is as follows: a solvothermal method is adopted, the Cu-doped W18O49 (xCu-W18O49) nano-enzyme is prepared by regulating and controlling the molar doping amount of a Cu element, taking tungsten chloride as a tungsten source, taking copper chloride dihydrate as a copper source and taking n-propyl alcohol as a reaction solvent. The crystallinity of the nano enzyme is good, and the nano enzyme shows remarkable glutathione oxidase (GSHOx) activity in a tumor microenvironment. Compared with W18O49, Cu doping enables enzyme activity to be remarkably improved, the problem of low activity generally existing in current cancer treatment nano-enzymes is effectively solved, and meanwhile the nano-enzyme has application potential in the aspect of CT imaging.

The invention relates to the field of bioengineering, in particular to an enzyme composition, a product and application of the enzyme composition in preparation of Ectoine. The invention provides an enzyme composition. The enzyme composition comprises a mutant of 2-hydroxy-4-aminobutyric acid oxidase, a mutant of keto transaminase, a mutant of hydroperoxide hydrolase, a mutant of Ectoine synthetase, a mutant of pyruvic acid-CoA oxidase and lactobacillus helveticus lactic dehydrogenase. According to the method disclosed by the invention, a plurality of mutant enzymes are utilized for combined transformation for the first time, and cheap 2-hydroxy-4-aminobutyric acid is taken as a starting raw material to quickly and efficiently produce Ectoine; the enzyme method has the characteristics of easiness in control, short conversion time, few generated impurities and the like, so that the method has unique advantages in the aspects of low-cost and large-scale mass production of Ectoin.

The invention discloses a porous CoFe hydrotalcite nano material as well as a preparation method and application thereof, and relates to the field of nano materials. The porous CoFe hydrotalcite nano-material is of a porous layered double hydroxide nano-structure, and the aperture of the porous CoFe hydrotalcite nano-material ranges from 2 nm to 10 nm. The porous CoFe hydrotalcite nano material is prepared through a microwave hydrothermal synthesis method, the preparation method is simple, easy to operate and environmentally friendly, and industrial production can be achieved. The porous CoFe hydrotalcite nano material prepared by the method is stable in structure, has photocatalytic activity and peroxidase-like activity, can effectively catalyze and generate various reactive oxygen free radicals under the illumination condition, realizes efficient synergistic killing of bacteria, and has a good antibacterial effect.

According to the preparation method disclosed by the invention, the whole fruit juice of the lonicera caerulea (which retains fruit residues) is fermented by virtue of the plant lactobacillus KLDS1.0391, KLDS1.0320 or KLDS1.0368, so that the xanthine oxidase (XO) inhibition activity is remarkably improved. After fermentation, the XO inhibition rate is increased to 48-50.87% (the content of unfermented juice is 31.21%), the total phenol content is increased by 15-24.3%, and the contents of main XO inhibitors in the lonicera caerulea: cyanidin-3-O-glucoside (IC50 = 115.28 [mu] M), cyanidin-3, 5-diglucoside (IC50 = 116.34 [mu] M), peonidin-3-glucoside (IC50 = 105.34 [mu] M), quercetin (IC50 = 88.75 [mu] M), catechin (IC50 = 110 [mu] M) and caffeoylquinic acid (IC50 = 250.35 [mu] M) are remarkably increased. Wherein the quercetin content is increased by 73.8% at most (KLDS1.0320 strain fermentation is performed for 24 hours), and the XO inhibition rate is increased from 31.21% to 50.87%. Technical support is provided for development of a natural XO inhibitor and a functional fermented beverage, so that a new thought is provided for functional fermented juice with lonicera caerulea as a key component.

The invention discloses escherichia coli recombinant bacteria with high glycolic acid yield and a construction method of the escherichia coli recombinant bacteria, and belongs to the technical field of bioengineering. Lactate dehydrogenase ldhA, phosphate transacetylase pta, acetokinase ackA and pyruvate oxidase poxB are knocked out in escherichia coli, key enzymes isocitrate lyase aceA and glyoxylate reductase ghrA in a glycollic acid synthesis path are over-expressed in a genome level, conversion of carbon flow to glycollic acid is enhanced, and the glycolic acid is converted into glycolic acid. On the basis, malic acid synthase AaceB, malic acid synthase GglcB and glycollic acid oxidase glcDEF are knocked out, a branch metabolic pathway is blocked, an efficient strain which is free of plasmids and resistance genes and does not need to induce glycollic acid production is constructed, the accumulation amount of L-valine fermented in a 5L fermentation tank for 48 hours reaches 51.2 g / L, the yield is 0.6 g / g, and the production intensity is 1.06 g / L / h.

The invention provides a tobacco polyphenol oxidase gene NtPPO15 and application of the tobacco polyphenol oxidase gene NtPPO15 in inhibiting browning of tobacco and improving ripening resistance and baking resistance of the tobacco. According to the invention, a key gene NtPPO15 related to tobacco browning and baking resistance is screened through experiments, the activity of an NtPPO15 promoter and a gene expression site are further explored by constructing a GUS dyeing vector, and the function of the gene is deeply studied through gene editing and overexpression. Experiments prove that the NtPPO15 gene provided by the invention is a key gene related to browning in a tobacco maturing and baking process, and by regulating and controlling the expression quantity of the NtPPO15 gene, the browning of the tobacco can be controlled, the maturing resistance and baking resistance of the tobacco can be improved, the quality of a tobacco product can be improved, the harvesting frequency can be reduced, and the economic benefit can be greatly improved; and the method can also be used for screening tobacco varieties with excellent quality, so that the method has a good and wide market application prospect.