13-34: Production of monomeric and oligomeric glucose during enzymatic hydrolysis of dilute-acid pretreated corn stover

For biochemical-based production of ethanol from lignocellulosic biomass, achieving high glucose yields from enzymatic cellulose hydrolysis is a critical performance factor affecting the process’s economic viability. In this study, we measured glucose yields during enzymatic cellulose hydrolysis of dilute-acid pretreated corn stover washed solids and on the whole pretreated slurry. Empirical models of monomeric glucose yield were generated as a function of total solids (10%-30%) and enzyme loadings (10-40 mg protein/g cellulose) using a face-centered response surface design. Enzymatic hydrolysis was performed with 100 grams of slurry in 250-mL capped Schott media bottles at 48°C using a commercially available enzyme preparation. As expected, glucose yields increased with decreasing solids loading and increasing enzyme loadings for either washed solids or whole slurries. We also observed that oligomeric glucose concentrations ranged from 2 -17 g/L representing between 6% and 10% of the total glucose released during enzymatic cellulose hydrolysis, and that oligomeric glucose concentrations were greater at the higher solids loadings. These findings demonstrate that either improved enzyme or alternative process strategies or both are necessary to reduce oligomeric sugars yields and thereby increase monomeric glucose production, especially at high solid loadings.