Production of organic acids by Lactobacillus strains in three different media

Abstract

Ten strains of Lactobacillus (Lb). casei, Lb. rhamnosus, Lb. plantarum, Lb. paracasei and Lb. curvatus species were chosen to determine the production of organic acids after cultivation in skimmed milk, MRS broth and Jerusalem artichoke (JA) medium. The highest acidity was obtained in MRS broth and the weakest acidification was found in skimmed milk. Lb. casei Shirota produced the highest amount and Lb. rhamnosus VT1 the lowest amount of substances being estimated as titratable acidity. All strains produced lactic acid in the investigated broth and most of the strains produced acetic acid in MRS broth except Lb. curvatus 2768 and Lb. casei Shirota, in JA broth except Lb. paracasei SF1 and in skimmed milk except Lb. casei 2750, Lb.curvatus 2768, Lb. curvatus 2775 and Lb. casei Shirota. All strains, except Lb. plantarum 01, produced butyric acid in MRS broth. Beside the lactic and acetic acids, formic, citric, succinic and glutamic acids were also produced in MRS broth; formic and succinic acids were produced in skimmed milk and succinic acid in JA broth. Some strains showed change in their fermentation profile from homofermentative to mix-acid fermentation in milk. The antifungal efficiency of the lactic and acetic acid in the amount produced by lactobacilli was investigated. None of the investigated aspergilli were inhibited. The inhibitory effect of acids against Fusarium increased unequivocally with the increasing concentration. The study pointed at the dissimilarity of organic acid production of Lactobacillus strains, which was considerably influenced by the media.