A Novel Promising Thermotolerant Cellulase-Producing Bacillus licheniformis 1-1v Strain Suitable for Composting of Rice Straw

Thirty nine thermotolerant cellulose decomposing bacteria were isolated from different natural sources. Amongst those, isolate 1-1v exhibited the highest avicelase, carboxymethyl cellulase and filter paperase activities at 50oC using rice straw as a sole carbon source. This isolate was identified as Bacillus licheniformis 1-1v based on morphological, physiological, biochemical characteristics using VITEK 2 system, and 16S rRNA sequence analysis. Factors affecting cellulase productivities and rice straw utilization were investigated. The optimum rice straw concentration, pH value and temperature for the highest cellulase production were 50 % (w/v), 6.0, and 50oC, respectively. Interestingly, the isolate showed high activity at a wide range of temperatures and pH values. The effect of some compost additives on cellulase production were also investigated. These additives include rock phosphate, feldspar, dolomite, and natural powder of iron, zinc, manganese salts, gypsum, lime and some nitrogen sources (sodium nitrate, ammonium sulphate, ammonium nitrate and urea). Amongst all, feldspar has significantly enhanced cellulase production. The highest cellulase production was obtained by supplementation of 0.75 % (w/v) of feldspare at 131.1 U/g-dry rice straw. The optimal inoculum size for cellulase production were 1 % that exhibited cellulase production at 139.4 ±6.76 U/g-dry rice straw compared to 20.8 U/g-dry rice straw before optimization (~ 7 folds increase) These result indicated the potentiality of the selected strain for rapid biodegradation of rice straw and its possible application in enhancement of composting process.