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.