The present invention is related to a recombinant host cell, in particular a yeast cell, comprising a dihydroxy-acid dehydratase polypeptide. The invention is also related to a recombinant host cell having increased specific activity of the dihydroxy-acid dehydratase polypeptide as a result of increased expression of the polypeptide, modulation of the FeS cluster biosynthesis of the cell, or a combination thereof. The present invention also includes methods of using the host cells, as well as, methods for identifying polypeptides that increase the flux in an FeS cluster biosynthesis pathway in a host cell.

Methods of screening for dihydroxy-acid dehydratase (DHAD) variants that display increased DHAD activity are disclosed, along with DHAD variants identified by these methods. Such enzymes can result in increased production of compounds from DHAD requiring biosynthetic pathways. Also disclosed are isolated nucleic acids encoding the DHAD variants, recombinant host cells comprising the isolated nucleic acid molecules, and methods of producing butanol.

Methods for the fermentative production of four carbon alcohols is provided. Specifically, butanol, preferably isobutanol is produced by the fermentative growth of a recombinant bacterium expressing an isobutanol biosynthetic pathway.

The invention provides an Escherichia coli for synthesizing L-valine, a construction method and use thereof. The Escherichia coli of the invention is designated as Escherichia coli W3110 and was deposited in China Center for Type Culture Collection (Address: Bayi Road, Wuchang District, Wuhan City, Hubei Province) under the Accession No. CCTCC M 2022293 on Mar. 18, 2022. The recombinant Escherichia coli takes Escherichia coli as a starting strain, and a transcription regulation factor is overexpressed to obtain a recombinant Escherichia coli. The recombinant Escherichia coli for synthesizing L-valine of the invention is fermented in a 5 L fermentor with trace dissolved oxygen to test strains, the yield of L-valine reaches 112 g/L, and the OD of the bacterium is 104.

The present invention relates to preparation of key drug intermediate, L-2-amino butyric acid (L-2-ABA) by a method of cell free system and biotransformation using genetically engineered strains from easily available economic substrates like citramalate or citraconate and enzymes like LeuCD, LeuB and ValDH or IlvE.

Genetically modified microorganisms that have the ability to convert carbon substrates into chemical products such as isobutanol are disclosed. For example, genetically modified methanotrophs that are capable of generating isobutanol at high titers from a methane source are disclosed. Methods of making these genetically modified microorganisms and methods of using them are also disclosed.

The present invention provides a genetically engineered pantoic acid-producing strain having or having an enhanced NADH-dependent acetohydroxy acid reductoisomerase, a method for producing the strain, a method for producing D-pantoic acid using the strain, and use thereof in production of D-pantoic acid.

The present invention provides a method for constructing an L-valine production strain, the L-valine production strain, and use thereof. According to the method for constructing the L-valine-producing strain, a 2,3-butanediol- or acetoin-producing strain is used as a starting strain, and genetic engineering modification is performed on the strain to improve the L-valine yield thereof. The present invention provides a new thought and way for efficient production of L-valine, and obtains a new production strain for efficiently producing L-valine. The L-valine-producing strain obtained in the present invention requires a simple culture medium and has low fermentation substrate and culture costs; meanwhile, the strain has a high L-valine yield and has a single product component easy to separate.

Multi-carbon compounds such as ethanol, n-butanol, sec-butanol, isobutanol, tert-butanol, fatty (or aliphatic long chain) alcohols, fatty acid methyl esters, 2,3-butanediol and the like, are important industrial commodity chemicals with a variety of applications. The present invention provides metabolically engineered host microorganisms which metabolize methane (CH.sub.4) as their sole carbon source to produce multi-carbon compounds for use in fuels (e.g., bio-fuel, bio-diesel) and bio-based chemicals. Furthermore, use of the metabolically engineered host microorganisms of the invention (which utilize methane as the sole carbon source) mitigate current industry practices and methods of producing multi-carbon compounds from petroleum or petroleum-derived feedstocks, and ameliorate much of the ongoing depletion of arable food source farmland currently being diverted to grow bio-fuel feedstocks, and as such, improve the environmental footprint of future bio-fuel, bio-diesel and bio-based chemical compositions.