Statistical optimization of alkaline hydrogen peroxide pretreatment of sugarcane bagasse for enzymatic saccharification with Tween 80 using response surface methodology

Abstract

Sugarcane bagasse is a byproduct constituting more than 25 % processed matter after cane juice extraction and is thus a low-cost renewable substrate for value-added products such as bioethanol and xylitol due to its high content of hemicellulose and cellulose. In this study, a Box–Behnken response surface method design was used to optimize alkaline hydrogen peroxide pretreatment of dilute acid-treated sugarcane bagasse. Hydrogen peroxide concentration (2–6 % w/v), pretreatment time (10–40 h) and liquid/solid ratio (8–20 v/w) were tested in order to maximize glucose production in the enzymatic hydrolysis process. The optimum conditions obtained were 4.7 % w/v hydrogen peroxide concentration, 26.7-h pretreatment time, and 17.1 v/w liquid/solid ratio, producing 31.1 g/L glucose (40.2 % glucose yield) at 72-h hydrolysis. After optimizing alkaline hydrogen peroxide pretreatment, a second Box–Behnken design was used to evaluate the effects of cellulase loading (3.4–5.6 filter paper unit (FPU)/g solid), β-glucosidase loading (15–27 beta-glucosidase unit (CBU)/g solid) and Tween 80 concentration (0.11–1.7 % w/v) on glucose production during enzymatic hydrolysis. By analyzing response surface plots and time course hydrolysis, 50.1 g/L glucose (64.8 % glucose yield) was obtained at 120-h hydrolysis using 4.1 FPU/g solids for cellulase, 18.2 CBU/g solids for β-glucosidase and 0.95 % w/v for Tween 80. This yield corresponds to a 29 % improvement in glucose concentration compared to no Tween 80 addition.