Investigating effects of high cellulase concentration on the enzymatic hydrolysis of the sisal cellulosic pulp

The goal of this study was to investigate how the use of high concentration of cellulase may impact the properties of the substrate and the reaction medium during the enzymatic hydrolysis of the sisal pulp. Enzyme concentration of 0.9 mL g⁻¹ was considered for hydrolysis of a sisal cellulosic substrate, and the results were compared with previous ones using 0.5 mL g⁻¹ as cellulase concentration. Nonhydrolyzed pulps and the liquors were withdrawn from the reaction medium and characterized by scanning electron microscopy, crystallinity index, average molar mass, length/thickness, and high-performance liquid chromatography (HPLC). The results indicated that the enzyme/substrate ratio impacted crystallinity variations during the reaction and the induction period for exoglucanase action. The concentration of 0.9 mL g⁻¹ led to a glucose yield (98%, an almost quantitative conversion) higher than 0.5 mL g⁻¹ (89%). Aiming to gain information on the post-burst phase (after 15 h), 1 g of sisal pulp was added, and the results demonstrated that the enzymes remained active, which can counterbalance the higher cost due to the use of high enzymes concentrations. This study deepened the understanding of the enzymatic hydrolysis of sisal cellulosic pulp, and the findings may also benefit investigations on other pulps.