الملخص الإنجليزي
Abstract
During composting, organic matter is degraded mainly by cellulolytic microorganisms at around 50°C. In this study, thermophilic cellulolytic Bacillus spp have been isolated from compost. Eight isolates showed cellulase activity by growing in Carboxymethylcellulose (CMC) broth. These isolates were able to degrade xylan and cellobiose. Among the eight isolates three isolates (B13B, B5Gb and B19G) showed the highest Carboxymethylcellulase (CMCase) activity. The maximum cellulase activity for B13b and B5GB occurred after microbial growth reached the stationary phase but the maximum activity of B19G was at the log phase after 4 h of incubation. It was found that reducing sugar liberated in media increased with the increase of CMCase activity for the three isolates. Moreover, significant correlation between cellulase activity and protein content was also observed. The crude cellulase from B19 strain showed activity toward CMC and filter paper but there was no detectable activity towards p-nitrophenyl- B-D-glucopyranoside (PNPG). The optimum temperature and pH for crude cellulase activity were 50°C and 6 respectively. Using API system the eight isolates were identified as Bacillus lentus, Geobacillus thermoglucosidasius and Bacillus firmus. However, using 16S rDNA sequencing all of the eight isolates were identified as .Bacillus licheniformis
