Production of acetone and acetaldehyde by lactic streptococci

Summary Seven strains of Streptococcus cremoris, four strains of Str. lactis, and one strain of Str. diacetilactis were examined for their ability to produce aldehydes and methyl ketones when grown in skim-milk. All strains were found to produce acetaldehyde and seven also produced acetone. No other aldehydes or methyl ketones were detected in any of the cultures. A method for the quantitative estimation of mixtures of aldehydes and methyl ketones by means of paper chromatography of their 2,4-dinitrophenylhydrazones is described.