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| The effect of pH adjustment on hydrolytic bacteria and methanogens during rumen fluid derived anaerobic digestion of rice straw |
| Received:November 22, 2017 |
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| KeyWord:rice straw;anaerobic digestion;pH adjustment;GH 5 hydrolytic bacteria;methanogens |
| Author Name | Affiliation | | DENG Yu-ying | Changzhou Vocational Institute of Engineering, Changzhou 213164, China | | RUAN Wen-quan | School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, China | | YU Li | Changzhou Vocational Institute of Engineering, Changzhou 213164, China | | HUANG Yi-bo | Changzhou Vocational Institute of Engineering, Changzhou 213164, China |
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| Abstract: |
| In order to evaluate the influence of pH adjustment on rumen-enhanced anaerobic digestion, this study investigates the hydrolytic and methanogenic characteristics in the semi-continuous mode. Microbial consortia were analyzed by relative quantitative PCR(Q-PCR) and MiSeq high-throughput sequencing technology. Compared with the control system, the methane yields after pH adjustment increases by 1.98-, 1.99-and 1.53-fold with three organic loading rates of 1.5, 3.5 g·L-1·d-1 and 7 g·L-1·d-1, respectively. The methane contents are significantly different from the control reactor(P<0.05), varying from 24% to 32%. Additionally, pH adjustment increases the ratios of acetate and propionate. The pH values vary from 6.24 to 7.77 in the digestion process, which are within the optimal range of methanogenesis from rice straw. Moreover, the FPase and CMCase activities show an increasing trend in the adjustment system. Microbial compositions of GH 5 hydrolytic consortia change significantly after anaerobic digestion. The relative abundances of Ruminococcus genus increase 12.47-fold compared with the ruminal inoculum, even though Clostridium was the predominant genus. The proportion of hydrogenotrophic Methanobrevibacter reaches 3.73% and the relative abundance of acetotrophic Methanosarcina also increases. Our results indicate that pH adjustment increases the efficiency of anaerobic digestion from rice straw through the enhancement of hydrolytic and methanogenic activities. |
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