ENZYMATIC-HYDROLYSIS OF CELLULOSE - AN OVERVIEW

Despite the fact that the world community is no longer preoccupied with fossil fuel shortages, there is still considerable research and development directed toward understanding and commercializing enzymatic hydrolysis of cellulose. These efforts have ranged from applied work on bioreactors to basic research focusing on the detailed molecular mechanisms of hydrolysis. Studies on cellulose pretreatment have provided considerable insights into the influence of crystallinity and specific surface area on the rate and extent of hydrolysis. In addition these studies have demonstrated that the economics of enzymatic hydrolysis processes can be significantly improved by pretreatment. However, the major drawback to commercialization of enzymatic hydrolysis processes continues to be the relatively low hydrolysis rates achieved and the high cost of the enzymes. Research efforts directed toward understanding and manipulating cellulase systems suggest that greater cellulase activity can be achieved through optimizing the mix of cellulases used in hydrolysis and through protein engineering of cellulases. Investigators are probing into the synergistic mechanisms observed in several cellulase systems in an effort to demonstrate that optimal combinations of cellulases can be obtained that will yield increased rates and extents of hydrolysis. These studies and other studies of cellulases have yielded considerable insights into the role that cellulase binding plays in synergism. Better understanding of the molecular mechanisms at work in hydrolysis will make it possible to use the revolutionary tools of cloning and site directed mutagenesis to modify cellulase systems so as to improve the conversion efficiency and economics of enzymatic hydrolysis processes.