Screening and identification of cellulose-degrading bacteria from soil and leaves at Kerman province, Iran

Cellulosic biomass is considered one of the most promising sources for the production of alternative renewable bioenergy and other valuable products. Identification and optimization of strains with high enzymatic activity that can overcome constraints imposed by the cellulosic structure is an essential step in the development of new biotechnologies. The aim of this study was to isolate and identify thermophilic (50 °C) and mesophilic (37 °C) cellulolytic bacteria from soil and leaves samples at Kerman, Iran. Degrader bacteria were isolated using serial dilution and pour plate method. Media contained carboxymethylcellulose (CMC), and filter paper was used as sources of carbon. Totally 22 mesophilic and 17 thermophilic bacterial strains which produced clear zones were further identified by morphological and biochemical tests. Screening of purified bacteria was performed to identify cellulase-producing bacteria by Congo red test. These bacteria were compared to each other based on cellulase activity, the percentage of growth, and extracellular protein amounts. The strains with the highest enzymatic activity were determined by the DNS method. The isolated US5 and US7 grew rapidly, and produced cellulase. The US5 created the largest clear zones (7 mm). Besides, these strains were selected for analysis of 16S rRNA sequence. The results showed that selected bacteria strains belong to Brevibacillus borstelensis. The B. borstelensis strains isolated in this study showed a suitable cellulase enzyme activity.