Provided is a mutant strain having improved aromatic amino acid production capability as a result of inactivation or weakening of activity of glutaminase which is expressed by glutaminase B (glsB) gene.

A method of generating a variant cyanobacterium (e.g., Synechococcus elongatus, in particular S. elongatus sp. PCC11801) for photoautotrophic production of an amino acid (e.g., L-phenylalanine); the variant so produced; a method of extending growth of a culture of a variant cyanobacterium and its photoautotrophic production of an amino acid; and a method of photo-autotrophically producing L-phenylalanine.

The present disclosure provides novel bacterial strains with altered expression or start codon modification of one or more RNA degradation/processing genes. The RNA degradation genes of the present disclosure are controlled by heterologous promoters. The present disclosure further describes methods for generating microbial strains comprising heterologous promoter sequences operably linked to RNA degradation/processing genes.

Disclosed is a mutant strain having improved aromatic amino acid production capability due to inactivation or weakening of activity of an FMN/FAD exporter protein which is expressed by yeeO gene.

The present invention provides a recombinant cell for producing para-nitro-L-phenylalanine (pN-Phe). The recombinant cell comprises heterologous genes encoding heterologous enzymes. The recombinant cell expresses the heterologous enzymes and contains a native metabolite. The native metabolite is converted to the pN-Phe in the recombinant cell. The biosynthesized pN-Phe may be incorporated into a target polypeptide in the recombinant cell without requiring exposure of the recombinant cell to exogenous pN-Phe. A cell culture comprising the recombinant cell is also provided. Further provided is a method of producing pN-Phe by a recombinant cell comprising heterologous genes encoding heterologous enzymes. The method comprises expressing a native metabolite by the recombinant cell, expressing the heterologous enzymes, and converting the native metabolite to the pN-Phe in the recombinant cell. The method may further comprise incorporating the pN-Phe into the target polypeptide in the recombinant cell.

Disclosed is a mutant strain having improved aromatic amino acid production capability as a result of the inactivation or weakening of activity of asparaginase which is expressed by ansB gene.

The present invention discloses a method for modifying an amino acid attenuator, a class of amino acid attenuator mutants, engineered bacteria created on the basis of the amino acid attenuator mutants, and use of the engineered bacteria. The present invention protects a method for relieving the attenuation regulation of an amino acid operon gene, which is modification of the amino acid operon gene by: removing a gene coding for a leader peptide and an anterior reverse complementary palindromic sequence in the terminator stem-loop structure, and maintaining a posterior reverse complementary palindromic sequence in the terminator. The amino acid operon particularly can be histidine operon, tryptophan operon, phenylalanine operon, alanine operon, threonine operon and etc. The present invention can be used for the production of amino acids and derivatives thereof in fermentation by bacteria, providing a novel method for improving the production of amino acids in fermentation.

Biomass (e.g., plant biomass, animal biomass, microbial, and municipal waste biomass) is processed to produce useful products, such as food products and amino acids.

Disclosed is an alcohol dehydrogenase mutant and application thereof in cofactor regeneration, and belongs to the technical fields of enzyme engineering and bioengineering. The alcohol dehydrogenase mutant is obtained by mutating valine at position 84 and/or tyrosine at position 127 in alcohol dehydrogenase having an original amino acid sequence as set forth in SEQ ID No. 1. The alcohol dehydrogenase mutant has high activity for a variety of alcohol co-substrates, and can catalyze these enzyme co-substrates for the regeneration of cofactor NADPH. Compared with the wild-type alcohol dehydrogenase KpADH, the alcohol dehydrogenase mutant has higher activity and catalytic efficiency, and for co-substrate 1,4-butanediol, its k.sub.cat value can be up to 75.9 min.sup.−1, its k.sub.cat/K.sub.m value can be up to 2009 min.sup.−1.Math.M.sup.−1, and its K.sub.m value can be as low as 11.3 mM. Therefore, the alcohol dehydrogenase mutant has a higher value in industrial application.

The present invention provides a method for producing an L-amino acid such as a branched-chain L-amino acid by fermentation using a bacterium of the family Enterobacteriaceae, particularly a bacterium belonging to the genus Escherichia, which has been modified to attenuate expression of the gshA gene.