The co-fermentation of syngas (mainly CO, H2 and CO2) and different concentrations of carbohydrate/protein synthetic wastewater to produce volatile fatty acids (VFAs) was conducted in the present study. It was found that co-fermentation of syngas with carbohydrate-rich synthetic wastewater could enhance the conversion efficiency of syngas and the most efficient conversion of syngas was obtained by co-fermentation of syngas with 5 g/L glucose, which resulted in 25% and 43% increased conversion efficiencies of CO and H2, compared to syngas alone. The protein-rich synthetic wastewater as co-substrate, however, had inhibition on syngas conversion due to the presence of high concentration of NH4+-N (> 900 mg/L) produced from protein degradation. qPCR analysis found higher concentration of acetogens, which could use CO and H2, was present in syngas and glucose co-fermentation system, compared to glucose solo-fermentation or syngas solo-fermentation. In addition, the known acetogen Clostridium formicoaceticum, which could utilize both carbohydrate and CO/H2 was enriched in syngas solo-fermentation and syngas with glucose co-fermentation. In addition, butyrate was detected in syngas and glucose co-fermentation system, compared to glucose solo-fermentation. The detected n-butyrate could be converted from acetate and lactate/ethanol which produced from glucose in syngas and glucose co-fermentation system supported by label-free quantitative proteomic analysis. These results demonstrated that the co-fermentation with syngas and carbohydrate-rich wastewater could be a promising technology to increase the conversion of syngas to VFAs. In addition, the syngas and glucose co-fermentation system could change the degradation pathway of glucose in co-fermentation and produce fatty acids with longer carbon chain supported by microbial community and label-free quantitative proteomic analysis. The above results are innovative and lead to achieve effective conversion of syngas into VFAs/longer chain fatty acids, which would for sure have a great interest for the scientific and engineering community. Furthermore, the present study also used the combination of high-throughput sequencing of 16S rRNA genes, qPCR analysis and label-free quantitative proteomic analysis to provide deep insights of the co-fermentation process from the taxonomic and proteomic aspects, which should be applied for future studies relating with anaerobic fermentation.

中文翻译：

---

通过与富含碳水化合物的合成废水共同发酵增强合成气厌氧转化为挥发性脂肪酸的微生物见解

本研究将合成气（主要是 CO、H2 和 CO2）与不同浓度的碳水化合物/蛋白质合成废水共同发酵生产挥发性脂肪酸（VFA）。研究发现，合成气与富含碳水化合物的合成废水共发酵可以提高合成气的转化效率，合成气与 5 g/L 葡萄糖共发酵获得的合成气转化效率最高，分别为 25% 和与单独使用合成气相比，CO 和 H2 的转化效率提高了 43%。然而，作为共底物的富含蛋白质的合成废水由于蛋白质降解产生的高浓度 NH4+-N (> 900 mg/L) 的存在而抑制了合成气的转化。qPCR 分析发现更高浓度的产乙酸菌，可以使用 CO 和 H2，与葡萄糖单独发酵或合成气单独发酵相比，存在于合成气和葡萄糖共同发酵系统中。此外，可利用碳水化合物和CO/H 2 的已知产乙酸梭菌在合成气单独发酵和与葡萄糖共发酵的合成气中富集。此外，与葡萄糖单独发酵相比，在合成气和葡萄糖共同发酵系统中检测到丁酸盐。在无标记定量蛋白质组学分析的支持下，检测到的正丁酸可以由合成气中的葡萄糖和葡萄糖共发酵系统产生的乙酸盐和乳酸/乙醇转化。这些结果表明，与合成气和富含碳水化合物的废水共同发酵可能是一种有前途的技术，可以提高合成气向 VFA 的转化率。此外，合成气和葡萄糖共发酵系统可以改变葡萄糖在共发酵中的降解途径，并在微生物群落和无标记定量蛋白质组学分析的支持下产生具有更长碳链的脂肪酸。上述结果具有创新性，可实现合成气有效转化为 VFA/长链脂肪酸，这肯定会引起科学和工程界的极大兴趣。此外，本研究还结合了 16S rRNA 基因的高通量测序、qPCR 分析和无标记定量蛋白质组学分析，从分类学和蛋白质组学方面提供了对共发酵过程的深入见解，应应用于与厌氧发酵相关的未来研究。