Can We Reduce the Cellulase Enzyme Loading Required To Achieve Efficient Lignocellulose Deconstruction by Only Using the Initially Absorbed Enzymes?

The cost-effective production of sugars from biomass continues to be challenging, partly due to the relatively high enzyme/protein loading required to achieve effective hydrolysis of the insoluble polysaccharides within the pretreated lignocellulosic substrates. Previous work has suggested that those enzymes that initially, strongly adsorb to the insoluble substrate are crucial for effective cellulose hydrolysis. However, most previous work in this topic area has used either purified enzymes or “older” generations of cellulase preparations acting on “model” cellulosic substrates. The results were, in several cases, contradictory or inconclusive. In the work reported here, the roles and functions of the initially adsorbed enzymes in determining the rate and extent of cellulose hydrolysis were assessed when using several different pretreated biomass substrates and the Novozyme enzyme preparation, Cellic CTec3. It was apparent that the initially adsorbed enzymes (irreversible bound to substrate after centrifugation) played a critical role as the removal of the “free/unadsorbed” enzymes in solution resulted in no significant decrease in the rate and extent of cellulose hydrolysis, regardless of the enzyme loading and the substrates used. By removing the initially, “free/unadsorbed” enzyme, the enzyme loadings required for an effective biomass deconstruction (>70% cellulose hydrolysis yields within 3 days) could be reduced by up to 50%, depending on the substrate used.