Abstract:

As a value-added bioproduct, biohexanol synthesis through biological way has attracted extensive attention. Although the cost of biohexanol can decrease using syngas as substrate, the low yield hexanol production limits its application. In this study, the advance of biohexanol production from wasted industrial syngas through biological fermentation is for the first time analyzed on the basis of recent studies. To date, only one strain is reported, which can convert syngas into biohexanol directly, being Clostridium carboxidivorans. This strain prefers to produce acetate, ethanol, butyrate and butanol rather than hexanol. The highest hexanol yield of Clostridium carboxidivorans was 1.06g/L. The performance of biohexanol fermentation can be influenced by several key environmental factors such as the composition of syngas, concentration of inhibitors, mass transfer efficiency of gas-solid, temperature and pH. Optimizing and regulating these parameters are helpful to improve the production of biohexanol. Coculture fermentation is an alternative way for biohexanol production using the bacteria such as C. ljungdahlii, A. bacchi and C. kluyveri, which can be separated into three steps: ①conversion of syngas into acetate and ethanol; ②caproate production from acetate and ethanol via chain elongation; and ③reduction of caproate into hexanol. However, the economic feasibility of coculture fermentation needs to be further proved. The future study will focuses on improving the low yield production of biohexanol which is considered as “bottleneck” issue. It is expected that the hexanol-producing bacteria with high productivity can be obtained through synthetic biology and genetic engineering.

Key words: syngas, anaerobic fermentation, Clostridium carboxidivorans, hexanol, biofuel

摘要：

己醇作为高附加值中链醇，其生物合成越来越受到研究人员的广泛关注。利用工业废弃合成气制备生物己醇能够降低原料成本，然而，生物己醇的低产率严重限制了其广泛应用。本文基于生物己醇发酵的新近报道，首次对合成气发酵制备生物己醇的研究进展进行了分析与综述。文中指出目前能够直接利用合成气合成生物己醇的菌株仅有Clostridium carboxidivorans一例，但其更倾向合成乙酸、乙醇、丁酸和丁醇等，其最高己醇产量仅为1.06g/L。己醇发酵性能受合成气组分、抑制物浓度、气液传质效率、温度和pH等影响，优化并调控关键环境因子有利于提高己醇产量。采用混菌发酵是生物己醇合成的另一种可替代途径，其关键三步反应为：①合成气向乙酸乙醇转化；②乙酸乙醇链延伸向己酸转化；③己酸还原为己醇，相关菌株包括C. ljungdahlii、A. bacchi和C. kluyveri等，然而混合发酵的经济性能有待进一步研究。文中指出未来生物己醇的研究将重点解决己醇产量低的“瓶颈”问题，通过合成生物学或基因工程手段改造并获得高产己醇菌未来可期。

关键词: 合成气, 厌氧发酵, Clostridium carboxidivorans, 己醇, 生物燃料