Effects Of Co²⁺ On Biogas And Microbial Community Structure In Anaerobic Fermention Of Cow Feces

The rural household anaerobic digesters have some problems such as long start-up, wasteful of materials, low efficient conversion and low gas production. On the basis of previous studies, this paper studied the effect of different concentrations of Co2+on anaerobic fermentation of cow feces. On the same time, archaeal and bacterial diversity and community structure were also analyzed by RFLP.The six concentrations of0、0.05、0.10、0.20、0.30and0.40mg·L-1·d-1Co2+in the batch anaerobic digesters were applied under room temperature.0mg·L-1·d-1Co2+is as control. The results showed that Co2+could improve the performance of anaerobic fermentation of cow feces and promote the production of biogas and methane. The production of biogas and methane was promoted at lower concentration but was suppressed at higher concentration. The biogas of0.05、0.10、0.20、0.30and0.40mg·L-1d-1Co2+were4.21%、10.49%、8.85%、8.97%and5.92%higher than the control.Phylogenetic and diversity analysis of archaea and bacteria showed that the community structures of archaea and bacteria were dynamic. Clone libraries were constructed for all three three periods (samples of total:13). The results showed that at early stage the dominant of archaea were Methanocorpusculum and Methanosarcina, at the middle stage the main archaea were Methanosarcina, Methanocorpusculum and Methanospirillum and at late stage Methanocorpusculum was dominant. There were a number of unknown groups of Crenarchaeota throughout the fermentation process. The diversity of archaea increased at the beging and then decreased. In the all period, the bacterial diversity was significantly higher than archaea and the dominant species were Clostridium at early stage, Protcobacteria, Baeteroidetes and Clostridium at the middle stage, Baeteroidetes, Protcobacteria and Clostridium at late stage. No significant effect of Co2+was observed on the community structure of archaea. The proportion of Clostridium and Protcobacteria increased when the concentration of0.10mg·L/-1·d-1Co2+ The result also showed that different concentrations of Co2+had no effect on archaeal, suggesting Co2+influence gas production by possibly influencing the key enzyme activy or changing the composition of relevant bacteria. This needs further study in the future.