Enzymatic Hydrolysis

Enzymatic hydrolysis is the most critical step in the bioconversion of lignocellulosic biomass to bioethanol. However, the structural complexity of recalcitrant biomass due to the steric orientation of the constituent polymers requires an efficient pretreatment step that brings about fractionation of complex structure into cellulose, hemicellulose, and lignin. The resultant slurry after pretreatment consists of toxic inhibitors and insoluble solid cellulose/lignin that negatively impact the catalytic performance of lignocellulolytic enzymes. Therefore, it becomes a major bottleneck for several upcoming biorefineries to achieve saccharification efficiency of less than 70% at high solid concentration (17–25%) with minimum enzyme loading. To overcome these challenges, catalytically active and robust carbohydrate-active enzymes (CAZymes) are a prerequisite for designing the lignocellulolytic enzyme cocktails that can overcome these challenges. This chapter reviews the current efforts to improve the enzymatic hydrolysis with specific emphasis on bioprospecting novel inhibitor-resistant enzymatic cocktails that are operational at high solid loading of pretreated biomass and capable of reducing the overall process cost.