Bioethanol production from the comparison between optimization of sorghum stalk and sugarcane leaf for sugar production by chemical pretreatment and enzymatic degradation

Abstract

This work reports the comparison of optimized pretreatment models on total sugar (TS) production from sugarcane leaf (SL) with sorghum stalk (SS) utilization to decompose the lignocellulosic biomass into oligosaccharide (OS). The accumulation variables were examined in the pretreatment model, including pretreatment time (1–3 days), concentrations of sodium hydroxide (NaOH) from 1 to 2% (w/v), and heating temperatures from 30 to 40 °C. TS productions were optimized by using response surface methodology (RSM) on central composite design (CCD) models. These models indicated excellent determination coefficients (R2) ranged from 0.9820 to 0.9900 and are significant. Process optimization showed that the highest TS yield was achieved of 32.612 g/L and 38.977 g/L for NaOH pretreatment at condition (2)% (w/v) NaOH at the temperature of 40 °C for 3 days. After pretreatment, the biomass was degraded using a cellulase enzyme to form the fermentable sugar for ethanol production by Saccharomyces cerevisiae TISTR5020. The maximum bioethanol yield of 8.374 ± 1.813 g/L was achieved at 2 days of fermentation time when compared with bioethanol yield (5.234 ± 0.907 g/L) of 4 days fermentation time.