Effect of Lignocellulosic Substrate and Commercial Cellulase Loading on Reducing Sugar Concentration for Ethanol Production

Fuel ethanol production from lignocellulosic biomass requires a relatively high initial sugar concentration in hydrolysate. Raising the substrate and enzyme concentration in the batch hydrolysis will normally help to heighten sugar concentration. In this study, dilute sulfuric acid pretreatment was used for chemical pretreatment of rice straw. The effect of rice straw and commercial cellulase (Accelerase 1000 TM ) loading were investigated. It was found that an increase in rice straw from 7.5 to 15.0 g/100 mL H2SO4 raised the reducing sugar concentration from 27.70 ± 1.72 to 58.42 ± 1.23 g/L. At the high level of rice straw up to 20.0 g/100 mL H2SO4 gave a slight increase in reducing sugar of 66.17 ± 0.00 g/L. On the contrary, the rice straw conversion decreased from 343.27 ± 1.29 to 286.22 ± 2.39 mg/g DS (Dry residue substrate) and holocellulose conversion slightly decreased from 47.02 ± 0.18 to 39.21 ± 0.33% (w/w) when the rice straw increased from 15.0 to 20.0 g/100 mL H2SO4. The reducing sugar concentration increased from 52.98 ± 0.73 g/L to 64.61 ± 0.53 g/L and rice straw conversion changed from 293.44 ± 5.12 to 414.16 ± 0.19 mg/g DS, when the use of Accellerase 1000 TM increased from 10 to 45 FPU/g DS. It also found that the large amount of Accelerase 1000 TM loading (50 and 55 FPU/g DS) did not improve the reducing sugar and rice straw conversion.