The present invention provides for a mechanism to reduce glycerol production and increase nitrogen utilization and ethanol production of recombinant microorganisms. One aspect of this invention relates to strains of S. cerevisiae with reduced glycerol productivity that get a kinetic benefit from higher nitrogen concentration without sacrificing ethanol yield. A second aspect of the invention relates to metabolic modifications resulting in altered transport and/or intracellular metabolism of nitrogen sources present in com mash.

The present invention relates to a recombinant nucleic acid molecule, a recombinant micro-organism, to a method for producing alanine and to the use of the recombinant nucleic acid molecule or the recombinant microorganism for the fermentative production of alanine.

Disclosed are a gene mining method combining functional sequence and structure simulation, an NADH-preferring phosphinothricin dehydrogenase mutant and an application thereof. The gene mining method comprises the following steps: (1) analyzing a characteristic sequence which an NADH-type glutamate dehydrogenase should have; (2) searching a gene library based on the characteristic sequence; (3) performing clustering analysis and protein structure simulation on genes obtained by the searching; (4) selecting genes that feature high gene aggregation and a protein structure similar to that of the known phosphinothricin dehydrogenase as candidate genes. A wild-type phosphinothricin dehydrogenase with an amino acid sequence as set forth in SEQ ID No.2 derived from Lysinibacillus composti is obtained through the gene mining, and then mutated, and an NADH-preferring phosphinothricin dehydrogenase mutant is screened out, which has a mutation site selected from one of the following: (1) A144G-V375F-M91A; (2) A144G-V345A-M91A; (3) A144G. This mutant enzyme can be used for catalytic reaction with an inexpensive coenzyme NAD.

Disclosed in the present invention is an L-glutamate dehydrogenase mutant, the sequence of the L-glutamate dehydrogenase mutant being a sequence in which amino acid residue A at position 175 in SEQ ID NO: 1 is mutated to be G, and amino acid residue V at position 386 is mutated to be an amino acid residue having less steric hindrance. Further disclosed in the present invention is an application of the described L-amino acid dehydrogenase mutant in the preparation of L-glufosinate-ammonium or a salt thereof. When the L-glutamate dehydrogenase mutant of the present invention is used to prepare L-glufosinate-ammonium or a salt thereof, compared to an L-glutamate dehydrogenase mutant in which only position 175 or 386 is mutated, the specific enzyme activity is higher. Therefore, the action efficiency of the enzyme is improved, reaction costs are reduced, and industrial production is facilitated.

The present invention provides for a mechanism to reduce glycerol production and increase nitrogen utilization and ethanol production of recombinant microorganisms. One aspect of this invention relates to strains of S. cerevisiae with reduced glycerol productivity that get a kinetic benefit from higher nitrogen concentration without sacrificing ethanol yield. A second aspect of the invention relates to metabolic modifications resulting in altered transport and/or intracellular metabolism of nitrogen sources present in corn mash.

Methods for increasing carbon-based chemical product yield in an organism by genetically modifying one or more genes involved in a stringent response and/or in a regulatory network, nonnaturally occurring organisms having increased carbon-based chemical product yield, and methods for use in production of carbon-based chemical products are provided.

Application of glutamate dehydrogenase GdhA of Peptostreptococcus asaccharolyticus in increasing the yield of poly-?-glutamic acid from Bacillus licheniformis. The glutamate dehydrogenase GdhA of the Bacillus licheniformis WX-02 per se is replaced with the glutamate dehydrogenase derived from the Peptostreptococcus asaccharolyticus by means of homologous recombination, which significantly increases the level of synthesizing the poly-?-glutamic acid for the Bacillus licheniformis, and the yield of the obtained poly-?-glutamic acid from strains is increased at least by more than 20% compared with control strains.

The present invention concerns a method for the production of derivatives of 4-hydroxy-2-ketobutyrate chosen among 1,3-propanediol or 2,4-dihydroxybutyrate by culturing a genetically modified microorganism for the production of the desired derivative of 4-hydroxy-2-ketobutyrate, the microorganism further comprising a gene coding for a mutant glutamate dehydrogenase converting by deamination L-homoserine into 4-hydroxy-2-ketobutyrate. The invention also concerns said genetically modified microorganism.

The present invention provides for a mechanism to reduce glycerol production and increase nitrogen utilization and ethanol production of recombinant microorganisms. One aspect of this invention relates to strains of S. cerevisiae with reduced glycerol productivity that get a kinetic benefit from higher nitrogen concentration without sacrificing ethanol yield. A second aspect of the invention relates tometabolic modifications resulting in altered transport and/or intracellular metabolism of nitrogen sources present in corn mash.

Disclosed are a phosphinothricin dehydrogenase mutant, a recombinant bacterium and a one-pot multi-enzyme synchronous directed evolution method. The phosphinothricin dehydrogenase mutant, with an amino acid sequence as shown in SEQ ID No.1, is obtained by mutating alanine at position 164 to glycine, arginine at position 205 to lysine, and threonine at position 332 to alanine in a phosphinothricin dehydrogenase derived from Pseudomonas fluorescens. The recombinant bacterium is obtained by introducing a gene encoding the phosphinothricin dehydrogenase mutant into a host cell. The host cell can also incorporate a gene encoding a glucose dehydrogenase or a gene encoding a formate dehydrogenase to undergo synchronous directed evolution to achieve double gene overexpression. The one-pot multi-enzyme synchronous directed evolution method of the present invention can screen recombinant bacteria with greatly improved activity. Compared with other catalysis processes such as the transaminase method, the method for preparing L-PPT of the present invention features relatively simple process, high conversion of raw materials of up to 100%, and high stereo selectivity.