Comparision of different pretreatments and optimization of simultaneous saccharification and fermentation in biobutanol production using corncobs

Abstract

Corncobs are one of the potential Thailand's agricultural biomass feedstocks for renewable energy, like biobutanol. Dilute sulfuric and phosphoric acid pretreatments have been successful developed for pretreatment to remove hemicelluloses and improve enzymatic hydrolysis. The optimum conditions of dilute sulfuric and phosphoric acid pretreatments were obtained at 120 ºC for 5 min with 15:1 liquid-to-solid (LSR) ratio and 140 ºC for 10 min with 10:1 LSR, respectively. Both of acid pretreatments gave the content of total sugar approximately 34-35 g/l. In case of inhibitor content (furfural), phosphoric acid pretreatment gives higher than sulfuric acid pretreatment. Characterizations of corncobs after pretreatment indicate that both of acid pretreatments can improve enzymatic accessibility and the better results present in pretreated corncobs with sulfuric acid in terms of surface area, crystallinity. To remove inhibitors, lime detoxification was carried out and resulted for significant improving Acetone-Butanol-Ethanol (ABE) production; however, furfural might not be the main inhibitor to C.berjerinckii. Simultaneous saccharification and fermentation (SSF) was applied to reduce inhibition of enzymatic hydrolysis. In addition, the condition of enzymatic hydrolysis and fermentation was obtained using Response Surface Methodology (RSM). The highest ABE of 11.82 g/I was obtained under optimum condition of pH 6.30, 35.7 ºC, and 61.2 h.