The aim of this study was to investigate how the microbial community structure adapts during the start-up phase and how the 13C fractionation of biogas reflects the microbial population dynamics in two parallel swine manure-fed anaerobic digesters. Two swine manure-fed reactors for the start-up of continuously stirred tank reactors at mesophilic condition were evaluated. Changes in community structure were monitored using 16S rRNA high-throughput sequencing to measure the abundance of fermenting bacteria and methanogens. Digesters with relatively stable Methanosarcinaceae started up successfully and contained high gas production and low levels of propionate. In contrast, the digester that experienced a difficult start-up period had reduced Methanosarcinaceae along with accumulated propionate and low gas production. Specific gas production, specific methane production, and 13C fractionation of biogas were influenced significantly by Methanosarcinaceae, Methanobacteriaceae, and Clostridiaceae, indicating that the 13C fractionation of biogas had significant potential to reflect microbial population changes and digester performance during the start-up period.

Department of Applied Ecology Faculty of Environmental Sciences Czech University of Life Sciences Prague Kamýcká 129 16500 Prague Czech Republic

Jiangsu Normal University Edinburgh University Centre for Transformative Biotechnology of Medicinal and Food Plants Jiangsu Normal University 101 Shanghai Road Xuzhou People's Republic of China Institute of Molecular Plant Sciences School of Biological Sciences University of Edinburgh King's Buildings Edinburgh EH9 3JH UK

The Key Laboratory of Biotechnology for Medicinal Plants of Jiangsu Province Jiangsu Normal University Road 101 Xuzhou 221116 Shanghai China Jiangsu Normal University Edinburgh University Centre for Transformative Biotechnology of Medicinal and Food Plants Jiangsu Normal University 101 Shanghai Road Xuzhou People's Republic of China

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