Purified cellulase-mediated simultaneous sugar utilization by Bacillus albus isolated from Similipal, Odisha, India

Among 24 isolated cellulolytic bacteria from Similipal Biosphere Reserve, the most efficient isolate was recognized as a strain of Bacillus albus. This strain of B. albus was evaluated for cellulase production and the cellulase activity was measured in submerged fermentation using substrate carboxymethyl cellulose (CMC). Different nutritional (carbon, nitrogen, and metal-ion sources) and physical variables (pH, temperature, substrate concentration, and incubation time) during the growth of B. albus were optimized to obtain maximum cellulase activity. The highest cellulase activity of 5.79 U/mL for B. albus was observed at pH 6.75, temperature 37.5°C, CMC concentration 8.5 g/L, and 42 h incubation time. Further, supplementation of glucose as a subsidiary carbon source, yeast extract, peptone as nitrogen sources, and MgSO₄ and MnSO₄ as metal-ion sources enhance the cellulase activity of B. albus. The purified enzyme was reported to have a molecular weight of ∼54 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A zymogram analysis evidenced the cellulase activity of the purified enzyme fractions obtained from diethylaminoethyl cellulose chromatography. The purified cellulase was reported to have an optimum pH and temperature of 7.0°C and 50°C, respectively with a capacity of retaining its 60% residual activity within pH 6.0-8.0 and temperature 30-40°C, respectively. The metal ions, K⁺ and Na⁺ were the activators, while Pb²⁺ and Hg²⁺ were the inhibitors for the purified cellulase. The purified cellulase showed K_m and V_max values of 0.38 M and 8.19 U/mL, respectively, in presence of the substrate CMC and also simultaneous consumption of both hexose and pentose sugars.