Agricultural and Biological Research

Production of bioethanol from free and immobilized cellulase produced by Bacillus subtilis BTSR1

Sunethra VM* and Rajakumar R

In the present situation, entire world is looking forward for an alternate energy source due to increased concern on environmental pollution and energy security. In the present aimed at the production of bioethanol by using free and immobilized cellulase from Bacillus sp. In this study, highest cellulase activity was expressed by the bacterial isolate identified as Bacillus subtilis BTSR1 (1.817 ± 0.26 U/mL) after 24 hr incubation at 37°C under static condition. In this study, the extracellular cellulose from B. subtilis BTSR1 strain was produced, purified and estimated to be 46 kDa with specific activity was 302.27 U/mg. Immobilization process was standardized with respect to concentration of CaCl2, sodium alginate and bead size in order to obtain maximum efficiency. Different percentages of sodium alginate gel were tried. However, maximum immobilization efficiency was achieved with 4% alginate with 0.2M CaCl₂ and bead size was 10 g. The resultant optimal conditions for the highest CM Case production by Bacillus subtilis under SSF using wheat bran and coffee pulp as substrates were used for the subsequent bioethanol production. Bioethanol production was further optimized by varying substrate concentration (1-5%), Yeast Extract (0.1-0.5%), pH (4-8) and time (2-10 days). Immobilized enzymes produced the highest yield of bioethanol 28 g/l was obtained for 4% of substrate concentration. Immobilized cellulase activity nearly doubled the amount provided from the free enzyme activity. Additionally yeast extract concentration also optimized and ethanol production was found to increase 27 g/l of 0.3% yeast extract concentration. pH and duration were optimized also play a remarkable role in the production of bioethanol. In this study concluded that the maximum amount of bioethanol production was observed in the immobilized enzyme than free enzyme. Thus, immobilized condition was improved the activity of enzyme to produced bioethanol.