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.