Abstract

The present study was carried out to isolate, enhancement, identification, optimization of cellulose-degrading bacteria present in sewage soil waste, and screening for potential antibacterial activity. Three bacterial isolates were cultured at a large rate by Minimal Salt Medium (MSM) and showed the highest cellulase activity determined by congo red and iodine assay on Carboxy Methyl Cellulose (CMC) agar plate. Then various culture parameters such as pH, temperature, incubation period, substrate concentration, carbon, and nitrogen sources were optimized for the maximum cellulase secretion. Based on the morphological, cultural, and biochemical tests, the isolated strains were identified as Bacillus licheniformis, Bacillus sp. and Pseudomonas chlororaphis respectively. Bacillus licheniformis compared to other strains produced the highest cellulase enzyme (1 µ/ml) determined by the DNS method at neutral pH and 40ºC temperature on 24 hours incubation period. This bacterial strain was screened for the antibacterial activity determination against several bacterial pathogens and generated an inhibition zone ranging from 12-21 mm. The ethyl acetate extract of the selected strain showed the potential antibacterial activity against Escherichia coli and moderate activity against Shigella boydii and Bacillus cereus. The Minimum Inhibitory Concentration (MIC) of the tested extract was observed to be in the range of 44-62 µg/ml. Based on optimization, cellulose degradation, and antibacterial activity, Bacillus licheniformis was the potential species among the strains. The strain from sewage soil waste can be helpful for biodegradation and industrial application.

Keywords: Licheniformis; Cellulase; Polysaccharide; Pseudomonas; Shigella