Fernández-Naveira Ánxela, Abubackar Haris Nalakath, Veiga María C, Kennes Christian
Chemical Engineering Laboratory, Faculty of Sciences, University of La Coruña, Rúa da Fraga 10, E-15008, La Coruña, Spain.
Appl Microbiol Biotechnol. 2016 Apr;100(7):3361-70. doi: 10.1007/s00253-015-7238-1. Epub 2016 Jan 25.
The fermentation of waste gases rich in carbon monoxide using acetogens is an efficient way to obtain valuable biofuels like ethanol and butanol. Different experiments were carried out with the bacterial species Clostridium carboxidivorans as biocatalyst. In batch assays with no pH regulation, after complete substrate exhaustion, acetic acid, butyric acid, and ethanol were detected while only negligible butanol production was observed. On the other side, in bioreactors, with continuous carbon monoxide supply and pH regulation, both C2 and C4 fatty acids were initially formed as well as ethanol and butanol at concentrations never reported before for this type of anaerobic bioconversion of gaseous C1 compounds, showing that the operating conditions significantly affect the metabolic fermentation profile and butanol accumulation. Maximum ethanol and butanol concentrations in the bioreactors were obtained at pH 5.75, reaching values of 5.55 and 2.66 g/L, respectively. The alcohols were produced both from CO fermentation as well as from the bioconversion of previously accumulated acetic and butyric acids, resulting in low residual concentrations of such acids at the end of the bioreactor experiments. CO consumption was often around 50% and reached up to more than 80%. Maximum specific rates of ethanol and butanol production were reached at pH 4.75, with values of 0.16 g/hg of biomass and 0.07 g/hg of biomass, respectively, demonstrating that a low pH was more favorable to solventogenesis in this process, although it negatively affects biomass growth which does also play a role in the final alcohol titer.
利用产乙酸菌发酵富含一氧化碳的废气是获取乙醇和丁醇等有价值生物燃料的有效途径。以羧基还原梭菌作为生物催化剂进行了不同的实验。在无pH调节的分批试验中，底物完全耗尽后，检测到了乙酸、丁酸和乙醇，但仅观察到可忽略不计的丁醇生成。另一方面，在生物反应器中，通过持续供应一氧化碳和调节pH，最初同时形成了C2和C4脂肪酸以及乙醇和丁醇，其浓度在此类气态C1化合物的厌氧生物转化中从未有过报道，这表明操作条件显著影响代谢发酵谱和丁醇积累。生物反应器中乙醇和丁醇的最大浓度在pH 5.75时获得，分别达到5.55和2.66 g/L。这些醇类既由CO发酵产生，也由先前积累的乙酸和丁酸的生物转化产生，导致生物反应器实验结束时这些酸的残留浓度较低。CO的消耗量通常约为50%，最高可达80%以上。乙醇和丁醇生产的最大比速率在pH 4.75时达到，分别为0.16 g/hg生物量和0.07 g/hg生物量，这表明低pH在此过程中更有利于溶剂生成，尽管它对生物量生长有负面影响，但生物量生长在最终醇类滴度中也起作用。
