Deconstruction of lignocellulosic biomass has vast potential for production of biofuels and bioproducts in biorefineries. However, this potential is currently not reached due to the recalcitrance of biomass to enzymatic degradation. Various pretreatment technologies have been developed to reduce the recalcitrance of biomass. Extractive Ammonia (EA) pretreatment is one such technology which alters the crystalline structure of cellulose from its native cellulose I to cellulose III allomorphic form which is more accessible towards enzymatic degradation. However, non-productive binding of cellulases to cellulose and/or lignin is still considered to be one of the key factors reducing the overall conversion efficiency of biomass to fermentable sugars. Previous reports have suggested that the dissociation of cellulases from cellulose surface could be one of the key rate-limiting steps in enzymatic degradation of cellulose, but this hypothesis has not been properly tested yet. Here, we have systematically correlated the binding affinity and binding kinetic rates of a library of engineered endocellulase mutants to the hydrolytic activity of the endocellulase on cellulose I and cellulose III. Interestingly, we saw that an increase in overall hydrolytic activity on cellulose I and cellulose III for all engineered cellulase mutants was tightly correlated with an overall reduction in cellulase binding affinity. We also characterized the binding kinetics of mutant carbohydrate-binding modules (CBMs), appended to the full-length cellulases, to cellulose I and cellulose III, in an effort to understand whether CBM-assisted cellulase dissociation is one of the key rate-limiting step in endoglucanase catalyzed hydrolysis of cellulose to soluble sugars.

Reducing non-productive binding of cellulases to improve crystalline cellulose hydrolysis rates

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.