Isolation, screening and optimization of β-glucosidase producing Bacillus sp. isolated from Egyptian environment and optimization of β-glucosidase producing Bacillus sp. isolated from Egyptian environment

Abstract

The aim of the present study is isolation, screening, identification and optimization of bacterial strains with high β-glucosidase activity from Egyptian soil environment. These strains were isolated and primary screened by growth in medium containing Carboxymethyl cellulose (CMC) for cellulases ability and the promising isolates were secondary analyzed for β-glucosidase and Endo-glucanase (Eg) activity. Among eight isolated strains, isolate (Eg 5) showed the highest β-glucosidase, Endo-glucanase activity and protein content 37.24 U ml^-1, 1.89 U ml^-1 and 220 µg/ml, respectively. According to morphological characteristics, the highest β-glucosidase producing isolate (Eg 5) identified as Bacillus sp. strain Eg 5, it was gram positive, bacilli, motile, facultative anaerobe and spore former. Based on biochemical tests and physiological studies, it was positive for Catalase, Oxidase, Citrate, nitrate reduction, Gelatin, H₂S production and esculin test, and negative for starch and casein hydrolysis. Also, the physiological studies it was grown at wide range of pH (5-9), with tolerance against NaCl concentration (1-5) % at high temperature 40°C. Different cultural, physical, and nutritional factors were studied for optimal production of β-glucosidase. Optimized conditions for β-glucosidase production were characterized as 1% inoculum size and pH 7 at 45℃ for 48 hours of incubation using cellobiose (1%w/v) as the best carbon source induced β-glucosidase production. Also, the nitrogen source Ammonium chloride at (1% w/v) was optimum for β-glucosidase production by this bacterium. This can contribute its β-glucosidase producing ability for industrial processes and biotechnological application.