Maximization of fermentable sugar production from sweet sorghum bagasse (dry and wet bases) using response surface methodology (RSM)

Abstract

Sweet sorghum bagasse (SSB) is an agroindustrial waste with a high fiber composition (34–44% cellulose, 25–27% hemicellulose, and 18–20% lignin), widely used in the production of second-generation biofuels. In this study, a response surface design (Box-Behnken) was used to optimize the enzymatic hydrolysis process, using Cellic CTec 3 enzyme. Treatment time (24–72 h), enzyme concentration (5–7% w/w), and liquid solid ratio (LSR) (5–9 v/w) were evaluated to maximize glucose production. The process was optimized both on a dry basis (solar radiation drying after each stage) and on a wet basis (continuous mode). The optimized conditions obtained in the enzymatic hydrolysis on a dry basis were 5% w/w enzyme concentration, 51-h treatment time, and 5: 1 v/w liquid solid ratio (LSR), obtaining 125.2 g/L glucose. For wet basis, the following results were obtained: 5% w/w enzyme concentration, 48-h treatment time, and 5: 1 v/w LSR, obtaining 148.64 g/L glucose. Optimized SSB on a wet basis showed an increase of 18.71% in glucose compared to that obtained on a dry basis, a reduction of 5.88% in process time, and elimination of 96-h solar drying, all of which favor continuous glucose production.