(800a) High-Titer and High-Yield n-Butanol Production From Lignocellulosic Biomass By Engineered Clostridium Tyrobutyricum

Fermentative n-butanol production by solventogenic clostridia usually suffers from low butanol titer, low butanol yield, and high substrate cost. In order to overcome these limitations, NADH driving force combined with adaptation and evolution mutagenesis strategy was used to achieve high-titer, high-yield, and cost-effective n-butanol production from lignocellulosic materials. In order to confirm that the C. tyrobutyricum mutant can consume glucose and xylose simultaneously and determine an optimal condition for n-butanol production from biomass hydrolysates, repeated-batch co-fermentation in a fibrous-bed bioreactor (FBB) using glucose-xylose mixture as a substrate was performed. Synchronized utilization of glucose and xylose with a high butanol titer (~ 20.0 g/L) and yield (> 0.30 g/g) was observed in the glucose-xylose co-fermentation. In addition, it is interesting to note that the consumption rate of xylose was dependent on glucose/xylose ratio. Then, the feasibility of using various cellulosic and lignocellulosic biomass hydrolysates, including Jerusalem artichoke, cassava bagasse, cotton stalk, sugarcane bagasse, soybean hull, and corn fiber, as alternative feedstocks for fermentative n-butanol production was investigated in both free-cell and immobilized-cell fermentation. The results showed that C. tyrobutyricum was capable of efficiently converting those biomass hydrolysates containing glucose and xylose to n-butanol, achieving a high titer of over 15 g/L and a high yield of over 0.30 g/g substrate. This study has demonstrated an economically competitive process for high-titer, high-yield, and cost-effective n-butanol production from abundant, renewable, and sustainable feedstocks.