Identification and lactic acid production of bacteria isolated from soils and tree barks

Abstract

The objective of this research was to isolate and identify lactic acid producing bacteria from soils and tree barks in Thailand. Their acid production was also determined. Methodology and results: Eleven bacterial strains isolated from soils and tree barks were screened for their lactic acid production. They were divided into 4 groups based on their phenotypic characteristics and 16S rRNA gene sequence analyses. Group I (3 isolates) identified as Lactococcus produced L-lactic acid ranged from 72.32 0.707-77.47 0.184 g/L, yield of 0.96 0.011-1.06 0.008 g/g, productivity of 1.00 0.010-1.08 0.003 g/L.h and optical purity was 100%. Group II (3 isolates) identified as Enterococcus hirae, produced L-lactic acid ranged from 31.56 0.424-34.86 0.283 g/L, yield of 1.06 0.008-1.23 0.036 g/g, productivity of 0.44 0.006-0.48 0.004 g/L.h and optical purity was 98.6-100%. Group III (3 isolates) identified as Bacillus coagulans, produced L-lactic acid ranged from 48.48 0.283-93.51 0.552 g/L, yield of 1.00 0.001-1.07 0.005 g/g, productivity of 0.67 0.004-1.30 0.008 g/L.h and high optical purity of the tested isolate was 99.56%. Group IV (2 isolates) identified as Sporoactobacillus. Only NN2 produced D-lactic acid concentration 87.64 0.375 g/L, yield of 0.83 0.000 g/g, productivity of 1.22 0.005 g/L.h and optical purity was 96.16%. All isolates produced lactic acid when 120 g/L of the initial glucose was used as a substrate. Conclusion, significance and impact of study: Lactic acid producing bacteria are isolated from soils and tree barks. The coccal isolates could produce high L-lactic acid concentration with high optical purity while the spore-forming isolates produces L-and D-lactic acid which are useful for food preservation, chemical in pharmaceutical, cosmetic and textile industries.