ABSTRACT
Five acid forming bacteria, SK3-3, SK3-6B, SK3-7B, SK13-3 and PL20-4S were isolated from soils collected in Samut Songkhram and Phitsanulok provinces. All isolates were Gram-positive, anaerobic, spore-forming, rodshaped bacteria. The isolates were screened for their end product fermentation and were identified based on their phenotypic characteristics and 16S rRNA gene sequence analyses. They were belonged to the genus Clostridium and were closely related to Clostridium butyricum DSM 10702T (99.7-100%) and Clostridium saccharoperbutylacetonicum N1-4T (98.0-98.2%) based on 16S rRNA gene sequence similarity. All 5 isolates were identified as Clostridium butyricum. They produced 4.51-8.90 g/L (19.40-54.82% yield) of L-lactic acid with 0.06-0.12 g/L/h productivity, 6.15-7.52 g/L of acetic acid and 24.32-29.67 g/L of ethanol as the end product fermentation.
ABSTRACT
The aim of this research was to study on the isolation and characterization of lactic acid producing bacteria in Thailand. Ten bacterial strains isolated from soils and plant bark and root were screened for their lactic acid production. They were divided into 7 groups based on their phenotypic and chemotaxonomic characteristics including 16S rRNA gene sequence analyses. Four isolates in Group I were identified as P. pentosaceus, and each isolate in Group II to Group VII was identified as Enterococcus casseliflavus, E. hirae, Lactobacillus. plantarum, L. paraplantarum, Bacillus coagulans and Sporolactobacillus terrae, respectively. The isolates in Group I, IV, V and VII produced DL-lactic acid ranged from 54.50-77.31 g/L (45.88-75.11% yield) and 0.76-1.07 g/L.h of productivity. The isolates in Group II, III and VI produced optically pure L (+)- lactic acid ranged from 60.72-89.34 g/L (70.00- 74.45% yield) and 0.84-1.24 g/L.h of productivity. B. coagulans isolate in Group VI could produce the highest optically pure L-lactic acid (99.75%).