Lactic acid bacteria have diverse shunts for the metabolism of acetald
ehyde, which is involved in the metabolism of carbohydrates, proteins
and nucleic acids. In Lactobacillus acidophilus and Lactobacillus case
i, strains isolated from feces of healthy children, acetaldehyde can b
e formed from different sources. Phosphotransacetilase, acetate kinase
, aldehyde dehydrogenase and 2-deoxiriboaldolase activities were found
in both strains. Alpha-carboxilase and threonine aldolase activities
only occurred in L acidophilus. In contrast, phosphoketolase activity
was present in L casei, but absent in the other strain studied. The ac
cumulation of acetaldehyde in the growth medium is possible because th
e enzymes specific activities to form it are higher than those able to
convert it to ethanol.