Succinic acid production from sucrose and sugarcane molasses by metabolically engineered Escherichia coli / 生物工程学报

Sugarcane molasses containing large amounts of sucrose is an economical substrate for succinic acid production. However, Escherichia coli AFP111 cannot metabolize sucrose although it is a promising candidate for succinic acid production. To achieve sucrose utilizing ability, we cloned and expressed cscBKA genes encoding sucrose permease, fructokinase and invertase of non-PTS sucrose-utilization system from E. coli W in E. coli AFP111 to generate a recombinant strain AFP111/pMD19T-cscBKA. After 72 h of anaerobic fermentation of the recombinant in serum bottles, 20 g/L sucrose was consumed and 12 g/L succinic acid was produced. During dual-phase fermentation comprised of initial aerobic growth phase followed by anaerobic fermentation phase, the concentration of succinic acid from sucrose and sugarcane molasses was 34 g/L and 30 g/L, respectively, at 30 h of anaerobic phase in a 3 L fermentor. The results show that the introduction of non-PTS sucrose-utilization system has sucrose-metabolizing capability for cell growth and succinic acid production, and can use cheap sugarcane molasses to produce succinic acid.

Effects of chemically modified sugarcane bagasse on butanol production by immobilized Clostridium acetobutylicum XY16 / 生物工程学报

Sugarcane bagasse modified by polyethylenimine (PEI) and glutaraldehyde (GA) was used as a carrier to immobilize Clostridium acetobutylicum XY16 in the process of butanol production. The effects of chemically modified sugarcane bagasse on batch and repeat-batch fermentations were investigated. Batch fermentation was conducted with an addition of 10 g/L modified sugarcane bagasse and 60 g/L glucose, resulting in a high solvent concentration of 21.67 g/L and productivity of 0.60 g/(L x h) with the treatment of 4 g/L PEI and 1 g/L GA. Compared to the fermentations by free cells and immobilized cells on unmodified sugarcane bagasse, the productivity increased 130.8% and 66.7%, respectively. The fibrous-bed bioreactor also maintained a stable butanol production during repeat-batch fermentations, achieving a maximum productivity of 0.83 g/(L x h) with a high yield of 0.42 g/g.