Screening and identification of thermophilic cellulolytic bacteria isolated from sawdust compost

Abstract

Composting process mainly depends on the metabolic pathways of the microorganism and involves the activity of different enzymes. Thermophilic cellulase-producing bacteria isolated from sawdust compost were tested for formation of a visible zone around the colonies on the agar plates medium containing carboxymethyl cellulose at 50ºC. Screening of carboxymethyl cellulase producing isolates was further realized on the basis in liquid medium by DNS method. Among 29 isolates investigated, V1 and V11 strains exhibited maximum enzyme activity of 1.9 and 2.3 U/mL, respectively. These isolates were selected for morphological, physiological and biochemical studies and 16S rRNA gene analysis. They were found a Gram-positive, rod-shaped spore forming cells, which were identified as Bacillus megaterium (V1) and Bacillus subtilis (V11) based on cell morphology, nucleotide homology and phylogenetic analysis. The optimal temperature for activity of endoglucanases (CMCase) ranged from 35–45°C (strain V1) and 40– 50ºC (strain V11). Our findings showed that Bacillus megaterium (V1) and Bacillus subtilis (V11) cellulase demonstrate thermophilic characteristics within wide range of temperature and meets the requirements for commercial enzymes.