Investigation of β-galactosidase production from Bacillus licheniformis VO2 and Bacillus licheniformis VO9 isolated from Bitlis Budaklı Hot Spring by solid phase fermentation method

In this study, a novel thermotolerant bacteria named strain VO2 and VO9 were isolated from hot spring mud sample in Bitlis (Budaklı). Based on morphological and biochemical tests, 16S rRNA gene sequence analysis, it was determined that isolates belonged to the Bacillus genus and were closely related to Bacillus licheniformis. The effect of different parameters such as incubation time, temperature, pH, carbon and nitrogen sources, metal salts and surfactants on β-galactosidase production was investigated by using solid state fermentation (SSF) method. Optimum production conditions for β-galactosidase under SSF, incubation time, temperatures, pH and solid substrate were found as 72, 45°C and, pH 7.0 and rice husk for VO2, they were found as 96 hours, 6.0, 40°C and lentil husk for VO9. The appropriate inoculum rate was 25% (1.816 ± 0.063 U/mg) for VO2 isolate and 30% for VO9 (1.494 ± 0.056 U/mg). In both isolates, among the various carbon sources tested, 1% lactose was found to be the best carbon source for enzyme production. As additional surfactants, 0,5% Triton X-100 enhanced β-galactosidase production. The β-Galactosidase, which was allowed to pre-incubate at 65ºC for 4 and 12 hours, maintained its activity for VO2 at a rate of 84% and 72%, while enzyme produced by VO9 maintained its activity at 60% and 48% under same conditions.