This work aimed to optimize the H2SO4-hydrolysis/pretreatment of sugarcane bagasse at 121 °C in a single-stage batch reactor and to investigate the effects of the acid concentration (0.159–1.841% w/v), reaction time (10–110 min) and solid-loading (4.89–30.11%). In this study a central composite rotatable factorial design was used to study the response pattern and to obtain the maximum xylose extraction from hemicellulose with minimum dissolution of cellulose. The considered optimum conditions were: H2SO4-solution concentration of 1.0% w/v, reaction time of 80 min and solid-loading equals 20%. Under these conditions, 76.04% of the total hemicellulose was removed and the hydrolysate contained (g/100gsugarcane_bagasse) 21.89 xylose, 1.81 arabinose, 5.42 glucose, 3.51 acetic acid, 0.20 furfural, 0.05 5-hydroxymethylfurfural and 0.09 levulinic acid. Pretreated material over optimum conditions (Figure 1) was evaluated by enzymatic digestibility at cellulase loading (15.0 and 6.7 FPU/gsubstrate ) and β-glucosidase loading (33.0, and 20.0 IU/gsubstrate) and solids substrate of 3, 5 and 8% (w/v). The highest total glucose yield after enzymatic hydrolysis (53.61%, 54.38% and 54.81%, at 3, 5 and 8% (w/v), respectively) was attained after 72 hours using 15.0 (FPU)/gsubstrate and 33.0 (IU)/gsubstrate. In conclusion, digestibility of the bagasse pretreated revealed that at optimum conditions investigated was reasonably effective for preparing the sugarcane bagasse for enzymatic digestibility since more than 75% of the hemicellulose was removed and 10.50% of cellulose was affected during pretreatment and digestibility about 62% were attained.
Figure 1. Micrograph of a fiber in sugarcane bagasse: (A) in nature and (B) pretreated at optimum conditions