The Conversion of Alpha-Ketoisovaleric Acid to Valine by Lactic Streptococci

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Abstract
Streptococcus lactis, Streptococcus lactis var. maltigenes and Streptococcus ere- moris were shown to possess active valine - glutamic acid trans-aminase systems, capable of converting alpha-ketoisovaleric acid to valine. In a chemically defined medium, the alpha-ketoacid filled the amino acid requirement of the test organisms. Cells of S. lac-tis var. maltigenes converted alpha-ketoisovaleric acid to 2-methyl-propanal, a flavorful aldehyde. Paper-chromatographic and flash-exchange gas-chromatographic methods were used to identify amino acids, neutral and acid carbonyl compounds.