Comparative evaluation of free and immobilized cellulase for enzymatic hydrolysis of lignocellulosic biomass for sustainable bioethanol production

Production of bioethanol from various lignocellulosic biomass through enzymatic hydrolysis is considered as a promising approach to fulfill the global energy demand. In addition to overcoming the worldwide energy crisis, it also plays an important role in the management of lignocellulosic waste. We have synthesized iron oxide nanoparticles (magnetic nanoparticles-MNPs) using cell filtrate of fungus, Alternaria alternata. The synthesis of MNPs was initially confirmed by the visual observation followed by characterization using different analytical techniques. The NTA and TEM analysis showed the average size of 47 and 55 nm respectively. XRD analysis confirmed the FCC structure of nanoparticles and zeta potential for MNPs was - 7.06 mV, which indicated the stability of nanoparticles. Further, comparative evaluation of enzymatic hydrolysis of lignocellulosic biomass (sugarcane bagasse) using free and immobilized cellulase on MNPs at different temperatures was studied. The results obtained demonstrated that, in first cycle of hydrolysis, free enzyme was more efficient which showed about 78% conversion of cellulose to glucose at 40 A degrees C after 24 h, whereas in case of immobilized enzyme it was found to be 72%. Moreover, immobilized cellulase was recovered by applying magnetic field and reused up to third cycle of hydrolysis. In second and third cycle, rate of conversion of cellulose to glucose was found to be 68 and 52% respectively. These findings suggest that immobilization of cellulase on MNPs facilitate the easy recovery and their reuse for more than one cycle of hydrolysis, thereby making the process economically viable. Further, optimization and modification of certain conditions will be helpful to increase the efficiency of immobilized enzyme.