11-11: Engineering carbohydrate binding modules for reduced lignin affinity

The high cost of hydrolytic enzymes is a barrier to the commercial production of lignocellulosic biofuels. One strategy for decreasing this cost is the recycling of enzymes in batch processes, or countercurrent enzyme adsorption for continuous or semi-continuous processes. Lignin is the second most abundant biomass component, making up 20-30% of biomass dry weight, and remains present in biomass after all industrially-relevant pretreatment methods. Numerous studies have demonstrated an inverse correlation between the rate of biomass hydrolysis and the lignin content. Lignin has been shown to inhibit enzymatic hydrolysis and enzyme recovery not only by physically blocking cellulose access, but also by nonproductively binding cellulases and contributing to enzyme denaturation.

Despite the numerous studies documenting cellulase adsorption to lignin, few attempts have been made to engineer enzymes for reduced lignin affinity. In this work, we are using phage display to engineer carbohydrate binding modules for reduced lignin affinity. Our selection attempts to identifies mutations that reduce lignin binding while retaining cellulose binding.