Citric Acid Fermentation by Streptococci and Lactobacilli

Abstract

Several spp. of homofermentative lactic acid bacteria, cocci and rods, utilize citric acid as an energy source for growth in the absence of fermentable carbohydrate. Fermentation balances with growing cultures of representative strains of en-terococci, Lactobacillus delbrueckii, and L. casei, have shown the main products in neutral cultures to be acetic acid and CO2, with formic and lactic acids accounting for most of the remaining C. Traces of acetylmethylcarbinol and ethyl alcohol were also formed. With citric acid as substrate, the fermentation products of the homofermentative lactic acid bacteria show several similarities to those formed by spp. of Leuconostoc and Aerobacter. Oxidized substrates, such as citric acid, will give more information as to the potentialities of the homofermentative organisms than will the more conventional hexoses.