The present disclosure relates to bacterium engineered to produce aromatic compounds or compounds with aromatic metabolites or intermediates using the CRISPR-CAS transcriptional activation (CRISPRa) and/or transcriptional repression (CRISPRi). Accordingly, in an aspect the present disclosure relates to an engineered bacterium comprising genetic elements supporting programmable transcriptional activation and/or repression. The present disclosure also provides methods and systems for producing aromatic compounds or compounds with aromatic metabolites or intermediates using the engineered bacterium disclosed herein.

Efficient production of a carboxylic acid is provided by a method of producing a carboxylic acid, which includes the following steps (A) and (B): (A) filtering a carboxylic acid-containing fermentation broth by passing said fermentation broth through a nanofiltration membrane, to obtain a carboxylic acid-containing filtrate from the permeate side of the membrane; and (B) extracting the carboxylic acid from the carboxylic acid-containing filtrate obtained in the step (A) using an extraction solvent which undergoes phase separation with the filtrate, and collecting a carboxylic acid extract phase-separated from the aqueous phase.

The present disclosure relates to an L-amino acid-producing E. coli mutant strain or Corynebacterium glutamicum mutant strain having enhanced L-amino acid productivity, and a method of producing L-amino acid using the same. The L-amino acid-producing E. coli mutant strain and Corynebacterium glutamicum mutant strain according to the present disclosure exhibit an enhanced ability to produce L-amino acid, such as L-tryptophan, L-phenylalanine, L-tyrosine, L-glutamine, L-lysine, L-arginine, L-valine, L-leucine, L-isoleucine, L-threonine, L-histidine, L-serine, or L-citrulline, compared to parent strains thereof, and are capable of producing a high concentration of L-amino acid in high yield.

Aspects of the invention relate to methods of producing small molecules for industrial application using natural organisms and engineered organisms.

A method is useful for the biocatalytic synthesis of proteinogenic L-amino acids, such as L-alanine, L-valine, L-methionine, L-leucine, L-isoleucine or L-phenylalanine from a respective aldehyde and carbon dioxide. In particular, the method is useful for the biocatalytic synthesis of L-methionine from 3-methylthio-propanal (methional) and carbon dioxide.

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.

Aspects of the invention relate to methods of producing small molecules for industrial application using natural organisms and engineered organisms.

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 bacterica, providing a novel method for improving the production of amino acids in fermentation

A method is useful for the biocatalytic synthesis of proteinogenic L-amino acids, such as L-alanine, L-valine. L-methionine. L-leucine, L-isoleucine or L-phenylalanine from a respective aldehyde and carbon dioxide. In particular, the method is useful for the biocatalytic synthesis of L-methionine from 3-methylthio-propanal (methional) and carbon dioxide.

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.