Assessment of different biomass feeding strategies for improving the enzymatic hydrolysis of sugarcane straw

This work describes improvements in the enzymatic hydrolysis of hydrothermally pretreated sugarcane straw. The experiments were performed in batch and fed-batch operation modes (50 mL and 3 L working volumes) with final solid loadings of 10, 20, and 30% (w/v) and enzyme dosage of 10 FPU/gsubstrate. The fed-batch assays showed the most promising results in terms of glucose production and cellulose-to-glucose conversion. In the experiments using a 3 L working volume, analysis of cellulose-to-glucose conversion, power consumption, and apparent viscosity showed that the best assays were those with smoother feed delivery (substrate plus enzyme) throughout the enzymatic hydrolysis. This strategy resulted in 108.8 g/L of glucose and cellulose-to-glucose conversion of 59.7%, corresponding to a final theoretical ethanol content of 55.6 g/L. The power consumption per unit volume and the apparent viscosity were less than 5 kW/m3 and 35 mPa s, respectively, throughout the hydrolysis. Thus, a more concentrated liquor and a less powerful motor to deliver power during the hydrolysis process were obtained in fed-batch strategy reducing the process energy costs.