Biochemical and physiological characteristics of lactic acid bacteria isolated from fermented plant biomass

The aim of work was isolation, selection and characterization of lactic acid bacteria strains capable of producing large amounts of L-lactate. 15 strains of thermophillic lactic acid bacteria were isolated from plant biomass subjected to spontaneous fermentation and characterized on the basis of their morphological, biochemical and phenotypic properties. Their ability for lactate formation was tested using Blickfeldt medium and in 10% reconstituted milk. All isolated strains were gram positive, catalase negative and on the basis of the biochemical properties they were classified to the following genera: Enterococcus faecium, Lactobacillus brevis, Lactobacillus pentosus, Lactobacillus fermentum and Lactobacillus plantarum. The analysis of the fermentative abilities revealed significant differences between the tested species of bacteria. Moreover, no strains with identical biochemical characteristics, even within the same genus, were identified. The examined strains produced from 1.6 to 30.2 g/L of lactic acid during 96 h of the fermentation process. The highest yield of lactic acid production was obtained for the strain of Lb. plantarum 5B and the lowest for Lb. pentosus 3B. The analysis of the fermentation products (lactic acid, acetic acid, ethanol) using the HPLC method allowed to divide the strains into two groups. All strains belonging to E. faecium and Lb. plantarum were classified as homofermentative, whereas the other strains were heterofermentative.