Enzymatic Hydrolysis of Steam-Treated Sugarcane Bagasse: Effect of Enzyme Loading and Substrate Total Solids on Its Fractal Kinetic Modeling and Rheological Properties

Rheological studies and fractal kinetic modeling were applied to investigate the enzymatic hydrolysis of steam-exploded sugarcane bagasse (195°C, 7.5 min) using Cellic CTec3 cellulases (Novozymes). Initially, a central composite rotatable design (CCRD) was performed to evaluate the effect of different enzyme loadings and substrate total solids (TS) on both substrate apparent viscosity and kinetic parameters of enzymatic hydrolysis. Hydrolysis at 20% TS for 12 and 96 h using 38.6 FPU g^-1 glucan released 52 and 110 g L^-1 glucose equivalents from the steam-exploded material, respectively, with cellobiose being always below 1.7% of these readings. Fractal kinetic modeling provided a good fit of both glucan and xylan conversions, and the fractal kinetic parameters k and h had a strong correlation with changes in both substrate TS and enzyme loading. At the center point of the CCRD, Cellic CTec3 caused a decrease of 1 order of magnitude in the substrate apparent viscosity at every 6 h of hydrolysis. Cellic HTec3 had a boosting effect on the enzymatic hydrolysis of cane bagasse glucans regardless of the low hemicellulose content of the steam-treated material. Glucan hydrolysis was improved by 8% when 10% Cellic HTec3 was added to a hydrolysis mixture containing Cellic CTec3 at 38.6 FPU g^-1 glucan. With this, a total production of 120 g L^-1 glucose was achieved at 72 h using 20% TS.