Oh Hyun Ju, Ko Ja Kyong, Gong Gyeongtaek, Lee Sun-Mi, Um Youngsoon
Clean Energy Research Center, Korea Institute of Science and Technology, Seoul, South Korea.
Division of Energy and Environment Technology, KIST School, University of Science and Technology (UST), Daejeon, South Korea.
Front Bioeng Biotechnol. 2022 Apr 25;10:850370. doi: 10.3389/fbioe.2022.850370. eCollection 2022.
The production of hexanol from syngas by acetogens has gained attention as a replacement for petroleum-derived hexanol, which is widely used in the chemical synthesis and plastic industries. However, acetogenic bacteria generally produce C2 compounds (e.g., acetate and ethanol) as the main products. In this study, the gas fermentation conditions favorable for hexanol production were investigated at different temperatures (30-37°C) and CO gas contents (30-70%) in batch gas fermentation. Hexanol production increased from 0.02 to 0.09 g/L when the cultivation temperature was lowered from 37 to 30°C. As the CO content increased from 30 to 70%, the CO consumption rate and hexanol production (yield, titer, and ratio of C6 compound to total products) increased with the CO content. When 70% CO gas was repeatedly provided by flushing the headspace of the bottles at 30°C, the total alcohol production increased to 4.32 g/L at the expense of acids. Notably, hexanol production (1.90 g/L) was higher than that of ethanol (1.20 g/L) and butanol (1.20 g/L); this is the highest level of hexanol produced in gas fermentation to date and the first report of hexanol as the main product. Hexanol production was further enhanced to 2.34 g/L when 2 g/L ethanol was supplemented at the beginning of 70% CO gas refeeding fermentation. Particularly, hexanol productivity was significantly enhanced to 0.18 g/L/day while the supplemented ethanol was consumed, indicating that the conversion of ethanol to acetyl-CoA and reducing equivalents positively affected hexanol production. These optimized culture conditions (gas fermentation at 30°C and refeeding with 70% CO gas) and ethanol supplementation provide an effective and sustainable approach for bio-hexanol production.
产乙酸菌通过合成气生产己醇作为石油衍生己醇的替代品已受到关注，石油衍生己醇广泛应用于化学合成和塑料工业。然而，产乙酸细菌通常以C2化合物（如乙酸盐和乙醇）作为主要产物。在本研究中，在分批气体发酵中，研究了在不同温度（30 - 37°C）和CO气体含量（30 - 70%）下有利于己醇生产的气体发酵条件。当培养温度从37°C降至30°C时，己醇产量从0.02 g/L增加到0.09 g/L。随着CO含量从30%增加到70%，CO消耗速率和己醇产量（产率、滴度以及C6化合物与总产物的比例）随CO含量增加。当在30°C下通过冲洗瓶顶空反复提供70%的CO气体时，总醇产量以酸为代价增加到4.32 g/L。值得注意的是，己醇产量（1.90 g/L）高于乙醇（1.20 g/L）和丁醇（1.20 g/L）；这是迄今为止气体发酵中产生的己醇的最高水平，也是己醇作为主要产物的首次报道。当在70% CO气体再进料发酵开始时补充2 g/L乙醇时，己醇产量进一步提高到2.34 g/L。特别是，在补充的乙醇被消耗时，己醇生产率显著提高到0.18 g/L/天，这表明乙醇向乙酰辅酶A和还原当量的转化对己醇生产产生了积极影响。这些优化的培养条件（30°C气体发酵和70% CO气体再进料）以及乙醇补充为生物己醇生产提供了一种有效且可持续的方法。
