Carbonyl Compounds Produced by the Growth of Lactobacillus bulgaricus

The carbonyl compounds produced by the growth of Lactobacillus bulgaricus on whey permeate supplemented with amino acids and on a defined medium were identified by reacting the media with 2,4-dinitrophenylhydrazine and separating the 2,4-dinitrophenylhydrazones by thin-layer chromatography. The 2,4dinitrophenylhydrazones of ketoacids were reduced to the corresponding amino acids and identified by thin-layer chromatography. Compounds identified were ketoacids corresponding to alanine, valine, isoleucine, threonine, and histidine; acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, benzaldehyde, phenyIacetaldehyde, glyoxal, methylglyoxal, dihydroxyacetone, diacetyl, levulinic acid, and acetonylacetone.