Metabolic engineering of amino acid production

The present invention is directed towards the fermentative production of amino acids, providing microorganisms, methods and processes useful therefor. Microorganisms of the invention are capable of converting glucose to amino acids other than L-isoleucine, L-leucine and L-valine with greater efficiency than the parent strain. The efficiency of conversion may be quantified by the formula: [(g amino acid produced/g dextrose consumed)*100]=% Yield and expressed as yield from dextrose. The invention provides microorganisms that are made auxotrophic or bradytrophic for the synthesis of one or more branched chain amino acids by mutagenesis and selected for their ability to produce higher percent yields of the desired amino acid than the parental strain. Preferred microorganisms are Corynebacterium, Brevibacterium or Escherichia coli producing L-lysine. Mutagenesis is performed by classical techniques or through rDNA methodology. Methods of the invention are designed to increase the production of an amino acid by mutagenizing a parental strain, selecting cells auxotrophic or bradytrophic for the synthesis of one or more branched chain amino acids and selecting branched chain amino acid auxotrophs or bradytrophs that produce a higher percent yield from dextrose of the desired amino acid than the parental strain. Processes of the invention are designed for the production an amino acid comprising culturing in a medium a microorganism obtained by mutagenizing a parent strain to be auxotrophic or bradytrophic for branched chain amino acid synthesis and selecting variants that are capable of converting glucose to amino acids other than L-isoleucine, L-leucine and L-valine with greater efficiency than the parent strain.