不同生境微生物转化H2/CO2产乙酸及其在合成气发酵中应用

Acetate production from H2/CO2 by mixed cultures from diverse ecosystems and their application for syngas fermentation

摘要:

【目的】合成气发酵对大力开发可再生资源和促进国家可持续发展具有重要意义，研究旨在探究不同生境微生物转化H2/CO2产乙酸及其合成气发酵的潜力。【方法】采集剩余污泥、牛粪、产甲烷污泥和河道底物样品在中温(37 °C)条件下生物转化H2/CO2气体，将来源于牛粪样品的H2/CO2转化富集物用于合成气发酵，通过454高通量技术和定量PCR技术分析复杂微生物群落的组成，GC气相色谱法检测气体转化产生的挥发性脂肪酸(VFAs)浓度。【结果】牛粪和剩余污泥微生物利用H2/CO2气体生成乙酸、乙醇和丁酸等，最高乙酸浓度分别为63 mmol/L和40 mmol/L，明显高于河道底物和产甲烷污泥样品的最高乙酸浓度3 mmol/L和16 mmol/L。牛粪和剩余污泥微生物中含有种类多样化的同型产乙酸菌，剩余污泥中同型产乙酸菌主要为Clostridium spp.、Sporomusa malonica和Acetoanaerobium noterae，牛粪中则为Clostridium spp.、Treponema azotonutricium和Oxobacter pfennigii。【结论】同型产乙酸菌的丰富度和数量两个因素都对复杂微生物群落转化H2/CO2产乙酸效率至关重要；转化H2/CO2得到的富集物可用于合成气发酵产乙酸和乙醇，这为基于混合培养技术的合成气发酵提供了依据。

Abstract:

[Objective] We studied acetate production from H2/CO2 by mixed cultures from diverse ecosystems and applied the system for syngas fermentation. [Methods] Undefined mixed cultures from waste activate sludge, freshwater sediment, anaerobic methanogenic sludge and cow manure were used for the bioconversion of H2/CO2 and enriched H2/CO2-converting cultures from cow manure were applied as inoculums for syngas fermentation. Gas and volatile fatty acids contents were measured by a gas chromatograph. We used 454 pyrosequencing and qPCR assay to reveal the community structure during the bioconversion. [Results] Acetate, ethanol and butyrate accumulated in cow manure and waste activated sludge during the incubation under H2/CO2 headspace with final acetate concentrations of approximately 63 mmol/L and 40 mmol/L, respectively, significantly higher than that of 3 mmol/L and 16 mmol/L in freshwater sediment and anaerobic methanogenic sludge. Diverse types of acetogens were found in waste activated sludge and cow manure. The major putative acetogens belonged to the species Clostridium spp., Sporomusa malonica and Acetoanaerobium noterae in waste activated sludge, and to Clostridium spp., Treponema azotonutricium and Oxobacter pfennigii in cow manure. [Conclusion] Both the richness and the number of acetogens were important factors for the bioconversion of H2/CO2 by mixed cultures. Enriched H2/CO2-converting cultures can use syngas as carbon source to produce acetate and ethanol.