Short-chain organic acids produced on glucose, lactose, and citrate media by Enterococcus faecalis, Lactobacillus casei, and Enterobacter aerogenes strains

Abstract

Three strains of Enterococcus faecalis, three of Lactobacillus casei and two of Enterobacter aerogenes, isolated from commercial Palmita-type cheese were cultured in peptone-yeast extract broth with glucose (PYG), lactose (PYL), or citrate (PYC) added as the main carbon sources. The short-chain volatile and non-volatile organic acids were extracted and their concentration determined by GC with a FID detector. The identity of the acids was determined by their retention times and confirmed by GC mass spectral (MS) analysis. Only acetic acid and propionic acid among the volatile acids, and lactic and succinic acids among the non-volatile acids, were found. Results showed that all the strains produced high concentrations of lactic acid from lactose (130–730 mg%); differences were mainly found among enterococci strains. Lactobacilli produced considerably higher quantities of lactic acid from glucose (1200–1300 mg%) compared to enterococci and Enterobacter strains. Acetic acid was produced in PYL only by enterococci strains and at very low concentrations (6–9 mg%). Both enterococci and Enterobacter strains produced relatively high concentrations of acetic acid in PYC (65–120 mg%). Succinic acid was only produced by the Ea 2 strain of E. aerogenes in both PYL (45 mg%) and PYC (40 mg%). Propionic acid was only produced in PYC (16 mg%) by the Ea 2 strain.