Cellulase: Critical Enzyme of Biofuel Industry – A Sea Water Based Approach

Abstract

Lignocelluloses are the most abundant biomass available on earth with immense potential to meet global energy demands in sustainable manner. Few key factors are involved in order to accomplish the same and cellulases play a pivotal role in this task. Cellulases are critical enzymes in biofuel and food industries. Several bacterial and fungal species have been reported to be the cellulase producer using different cellulose sources. Utilization of fungal strains has some advantages over bacterial strains as cellulase producers. Likewise there are many reports published which studied the utilization of cellulases for saccharification of bioreserouces for production of biofuels. However, all these works have been carried out using fresh water as a source of medium. Recent public threats on fresh water depletion signify the exploration of non-freshwater medium for the production of biofuels. Among the non-freshwater sources, seawater is the best source to be studied as medium for biomass conversion due to its abundant availability in India. Utilization of halotolerant microorganisms capable of producing salt tolerant enzymes will be a major breakthrough in this field as they can tolerate high salt levels and ionic liquids better than current fungal cellulases. Further, there will be advancement in use of sea and brackish water for biomass conversion. The present study focuses on isolation and screening of both bacterial and fungal strains from coastal zones of Odisha, capable of producing halotolerant cellulases. All the isolates were screened for their cellulolytic ability and their enzymatic properties were characterized using soluble cellulose sources in fresh as well as in seawater. The potent bacterial and fungal strains were characterized for different parameters like optimal pH and temperature of enzyme action along with effect of metal catalyst. For the bacterial cellulases the optimal pH was found to be at physiological pH whereas in case of a potent fungal cellulase isolated from paddy field was found to stable over a wide range. Optimal temperature of enzyme action in case of bacterial cellulases was recorded to be between 45-55˚C whereas in case of its fungal counterparts was found to be thermostable i.e. stable at 85˚C. Manganese ions used as cofactor played outstanding role in enhancing the potential enzyme activity manifolds compared to the one without cofactors. All the enzymes from different isolates have been partially purified and future work include their complete purification and active site determination for further studies and implementation on larger scale.