Abstract:
The isolation and screening of one hundred and ninety seven lipase-producing bacteria from 56 fermented food samples including sai-krog-prieo, nham, pla-ra, pla-chao, pla-chom, kung-chom and mum were carried out. The results revealed that 60 isolates showed lipase activity ranged from 0.01 - 21.52 U/ml. On the basis of their phenotypic characteristics and 16S rRNA gene sequence analysis, 14 isolates of Gram-positive cocci belonged to genera Staphylococcus (13 isolates) and Micrococcus (1 isolate) were identified as Staphylococcus sp. (6 isolates), S. sciuri (2 isolates), S. condiment (2 isolates) and each isolate of S. simulans, S. lentus, S. gallinarum and Micrococcus yunnanensis based on 99.55 – 100 % sequence similarity. Eleven isolates of Gram-positive rod shaped belonged to genera Bacillus, Paenibacillus, Brevibacterium and Corynebacterium were identified as B. cereus (2 isolates) and each isolate of B. methylotrophicus, B. pumilus, B. flexus, B. subtilis, B. anthracis, Paenibacillus pasadenensis, Brevibacterium salitolerans and Corynebacterium liquefaciens based on 99.33 – 100 % sequence similarity. Eleven isolates of Gram-negative rod shaped were identified as Proteus mirabilis (9 isolates) and Klebsiella pneumonia (1 isolate) based on 99.78 – 100% sequence similarity). In addition, 26 isolates of lactic acid bacteria were identified as Lactobacillus pentosus (5 isolate), Lactobacillus sp. (12 isolates), Pediococcus sp. (3 isolates) and each isolate of Pediococcus pentosaceus, Pediococcus lolii, Weissella thailandensis, W. cibaria, W. paramesenteroides and Leuconostoc fallax based on sequence 99.78 – 100 % similarity. The potent isolate KM17-4 identified as Staphylococcus condimenti was selected to determine on the effects for lipase production. The results revealed that KM17-4 exhibited high lipase activity on Tween 80 at pH 7, 30 Cº and incubated for 18 h. In addition, B. subtilis SS48-5 exhibited 3.23 U/ml of the highest activity when cultivated on Tween 80 at pH 7.5 for 24 h. The optimum temperature for lipase production of this strain was at 40 ˚C after incubated for 30 h. Whereas, Proteus mirabilis PR11-3 exhibited 0.57 U/ml of the highest lipase production activity and the optimum temperature was at 37 ˚C, pH 8 after incubated for 18 h.