Bioethanol generated from biomass is a promising alternative for fossil fuel substitute in near future. Agricultural residue is chosen due to global availability whole year and not competing with feedstocks. Although the material considered as inexpensive, the challenge is to make production cost lower with current technology. Bioethanol production from lignocellulosic biomass processed through three major steps: treatment before hydrolysis, hydrolysis and fermentation. Treatment methods intended for breaking the matrix of cellulose, hemicelluloses, and lignin for efficiency in next step of the process.
Thermochemical treatment methods are chosen to treat corn stalks powder using H2SO4, NaOH and H2O2 with concentrations ranging from 1-5%, temperature 121˚C for 20 min. Subsequently, treated powder will go through enzymatic hydrolysis using commercial cellulase and β-glucosidase in two stages and the effects of these treatments on enzyme hydrolysis and kinetics are compared. Two different fermentation: Separate Hydrolysis and Fermentation (SHF) and Simulaneous Saccharification and Fermentation (SSF) were employed to achieve the best ethanol yield.
Commercial cellulase used in this experiment has Km value of 70.03 mg/ml, Vmax 0.21 mg/ml/min and specific activity 1.69 FPU/mg. While for β-glucosidase maximum reaction rate (Vm), Km and specific activity are 8.94 mM/min, 127.06 mM, and 1.83 U/mg, respectively. Both enzyme achieved optimal condition at pH 5 and 60˚C. Corn stalk powder treated with 3% sulfuric acid produced reducing sugars 376.7±2.31 mg/g corn stalk powder after two-stage enzyme hydrolysis and SHF resulted in 92.21±4.8 mg ethanol/g corn stalk powder (2.09±0.18 % v/v), the highest compare to other treatments. The results suggest that the optimal condition for corn stalk powder was to treat with 3% H2SO4 and followed by two-stage enzyme hydrolysis at 60˚C in pH 5 for 48 hr and SHF.