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 bradytrophic for the synthesis of valine by mutagenesis.