摘要
合成气(主要包括CO、H_2和CO_2)通过生物转化生产高附加值的生物燃料和化学品已引起人们广泛关注,微生物菌群作为生物转化的酶催化剂对合成气发酵产物组成和效率十分关键.通过富集得到高温条件下分别稳定转化CO、甲酸钠和合成气的厌氧菌群,探究CO与甲酸钠转化菌混培物和合成气转化菌发酵合成气生成乙酸的能力,并分析其微生物群落结构.结果显示,CO-甲酸钠转化菌混培物与合成气转化菌在合成气发酵前期主要进行CO的产氢反应生成H_2和CO_2以及同型产乙酸反应生成乙酸,CO利用率为100%,CO反应速率分别为6.93和6.34 mmol L~(-1)d~(-1);随后同型产乙酸菌利用H_2和CO_2继续合成乙酸,两者的乙酸最大累积量分别为9.11 mmol/L和8.01 mmol/L.CO-甲酸钠转化菌混培物主要菌群为Thermoanaerobacterium、Romboutsia、Ruminococcus、Clostridium、Eubacterium、Moorella和Desulfotomaculum属,合成气转化混菌则主要含有Romboutsia、Thermoanaerobacterium、Moorella、Eubacterium、Acetonema和Clostridium属,其中同型产乙酸菌广泛分布于Ruminococcus、Clostridium、Eubacterium、Moorella和Acetonema属.本研究表明复配CO和甲酸钠转化菌可用于合成气高温发酵产乙酸,且转化能力优于合成气转化菌,结果可为合成气混菌发酵提供微生物资源和技术参考.
Syngas is a mixture of mainly CO, H_2, and CO_2, which can be produced from the gasification of various organic materials. Syngas fermentation has attracted great attention for its ability to produce valuable biofuels and biochemicals. As biocatalysts for syngas fermentation, microorganisms are important to product profile and conversion efficiency. In this research,the thermophilic CO-, formate-and syngas-converting microorganisms were enriched from cow manure, and the capability for acetate production from syngas by the CO-and formate-converting bacteria mixture and syngas-converting bacteria, as well as their microbial communities, were analyzed. The results showed that the CO-driven hydrogenogenesis and acetogenesis occurred during the initial stage of syngas fermentation and resulted in the formation of H_2 + CO_2 and acetate, respectively. The CO conversion efficiency was 100%, and the CO conversion rates of the CO-and formate-converting bacteria mixture and syngasconverting bacteria were 6.93 and 6.34 mmol L~(-1) d~(-1), respectively. Subsequently, H_2 + CO_2 was mainly converted into acetate via the acetogenic Wood-Ljungdahl pathway, and the final accumulation of acetate for the Co-and formate-converting bacteria mixture and syngas-converting bacteria were 9.11 and 8.01 mmol/L, respectively. The bacterial genera Thermoanaerobacterium,Romboutsia, Ruminococcus, Clostridium, Eubacterium, Moorella, and Desulfotomaculum dominated in the CO-and formate-converting bacteria mixture, and Romboutsia, Thermoanaerobacterium, Moorella, Eubacterium, Acetonema, and Clostridium were the main genera comprising the syngas-converting bacteria; among these genera, Ruminococcus, Clostridium,Eubacterium, Moorella and Acetonema harbor known homoacetogenic species. It is shown that the mixture of CO-and formateconverting bacteria can be used for thermophilic syngas fermentation, and its conversion ability is higher than that of the syngasconverting bacteria. This study identified potential microorganism resources and provides technical references for valuable chemicals and bioenergy production by syngas mixed-culture fermentation.
引文
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