(191z) N-Butanol Production from Cotton Stalk Using Engineered Clostridium Cellulovorans

Cotton stalk (CS) is a potential biomass for n-butanol production, but pretreatment and enzymatic hydrolysis are essential steps to obtain fermentable sugars because of the recalcitrant nature of lignocellulose, which usually results in a high operational cost. In this study, a consolidated bioprocess (CBP) was developed using a metabolically engineered Clostridium cellulovorans adhE2. First, various saccharides as substrates for n-butanol production by Clostridium cellulovorans adhE2, including glucose, xylose, cellulose, xylan, and xylooligosaccharide, were investigated. The results showed that n-butanol can be produced from all substrates studied, including cellulose and xylan.. However, faster growth appeared in media containing glucose and xylose. Second, various methods for the pretreatment of CS, i.e. dilute sulfuric acid pretreatment (DSAP), high pressure-assisted alkali pretreatment (HPAP), and high temperature water pretreatment (HTWP), and subsequent n-butanol fermentation from pretreated CS, without enzymatic hydrolysis, were explored. It was found that the intact structures of pretreated CS were obviously disrupted. The lignin of biomass was largely removed and the crystallinity of cellulose decreased after pretreatments. HPAP led to the highest reducing sugar and n-butanol yields compared to UAAP and HTWP. Finally, the engineered C. cellulovorans adhE2 produced n-butanol with a final concentration of >2 g/L and yield of >0.09 g/g from pretreated CS in CBP. This study demonstrated that the fermentation process with the engineered C. cellulovorans enabled a high n-butanol production directly from lignocellulosic biomass.