(231n) Enhanced N-Butanol Fermentation By Engineered Clostridium Tyrobutyricum Integrated with Gas Stripping

Butanol can be produced by acetone-butanol-ethanol (ABE) fermentation from lignocellulosic biomass such as soybean hull and sugarcane bagasse. Traditional ABE fermentation usually suffers from low butanol titer, yield and productivity, which however, can be boosted by applying external driving forces to redirect the electron and carbon flow towards butanol synthesis instead of byproduct formation. In this work, an engineered strain of Clostridium tyrobutyricum with ack knock out overexpressing adhE2 was used for butanol production from various carbon sources including glucose and xylose. Increased butanol production with high yields (>0.30 g/g) was achieved by providing artificial electron carrier such as methyl and benzyl viologen. Fed-batch fermentation in a fibrous-bed bioreactor integrated with gas stripping gave a total butanol production of 24.7 g/L, yield of 0.32 g/g and productivity of 0.10 g/Lâ??h from glucose/xylose mixture. The process produced 12.1 g/L butanol at a yield of 0.25 g/g and productivity of 0.12 g/Lâ??h from soybean hull hydrolysate (SHH), and 10.7 g/L butanol at a yield of 0.31 g/g and productivity of 0.081 g/Lâ??h from sugarcane bagasse hydrolysate. This work demonstrated the feasibility of producing biobutanol from low-cost agricultural residues such as soybean hull and sugarcane bagasse.