CHARACTERIZATION OF CRUDE THERMOSTABLE CELLULASE FROM GEOBACILLUS KAUSTOPHILUS STRAIN SBKS0103 AND ITS APPLICATION AS AN ANIMAL FEED ADDITIVE

A thermophilic bacterium strain SBKS0103 was isolated from sediments of the Boeklueng hot spring in Thailand and identified as Geobacillus kaustophilus based on 16S rRNA and confirmed by phylogenetic analysis. The result showed that crude cellulase production was highest after 2 days on carboxymethyl cellulose (CMC) medium at 55°C. The most favorable conditions of the crude enzyme were found to be at pH 6 and a temperature of 70°C. The protein profile of crude enzyme exhibited the endoglucanase activity at a molecular weight of around 63 kDa as determined by SDS-PAGE and zymogram analysis. For stability, crude cellulase retained 75% of its activity at 40°C and 20% at 70°C after 2 h of incubation. Enzymatic digestion of animal feed ingredients (untreated cassava pulp or sorghum seed) was performed at 37°C for 24 h. At pH 3, the dry weight reductions of cassava pulp and sorghum seed were 7.10±0.21% and 10.34±0.17%, respectively, and at pH 6, they were 11.63±4.32% and 12.71±1.44%, respectively. Moreover, reducing sugar concentration increased gradually since 2 h of incubation which confirmed the enzymatic degradation. In conclusion, crude thermostable cellulase from Geobacillus sp. has the potential to be developed as an animal feed additive to facilitate lignocellulose digestion.