Effects of different carbon sources on methane production and the methanogenic communities in iron rich flooded paddy soil

• Published in: The Science of the total environment Vol. 823; p. 153636
• Main Authors: Luo, Dan, Li, Yaying, Yao, Huaiying, Chapman, Stephen J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2022
• Subjects: acetates; carbon; climate change; environment; genes; glucose; High-throughput sequencing; Iron reduction; methane; methane production; Methanobacteriales; Methanogen; methanogens; Methanosarcinales; Organic matter; paddies; paddy soils; rice; Rice paddy; starch; Organic matter; Iron reduction; High-throughput sequencing; Methanogen; Rice paddy
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.153636

Various carbon sources as substrates and electron donors can produce methane via different metabolic pathways. In particular, the methane produced by rice cultivation has a severe impact on climate change. However, how Fe3+, the most abundant oxide in paddy soil, mediates the methanogenesis of different carbon sources is unknown. In this study, we investigated the effect of four carbon sources with different chain lengths (acetate, glucose, nonanoate, and starch) on CH4 production and associated methanogens in iron-rich paddy soil over 90 days of anaerobic incubation. We found that glucose and starch were the more preferential substrates for liberating methane compared to acetate, and the rate was also faster. Nonanoate was unable to support methane production. Methanosarcinales and Methanobacteriales were the most predominant methanogenic archaea as shown by 16S rRNA gene sequencing, though their abundance changed over time. Additionally, a significantly higher content of iron-reducing bacteria was observed in the glucose and starch treatments, and it was significantly positively correlated with the copy number of the methanogenic mcrA gene. Together, we confirmed the methanogenic capacity of different carbon sources and their related microorganisms. We also showed that iron oxides play a central role in regulating methane emissions from paddy soils and need more attention to be paid to them. [Display omitted] •The methanogenic capacity of glucose and starch were stronger than acetate.•Methanosarcinales and Methanobacteriales were mainly responsible for CH4 production.•The type and abundance of methanogens changed with the incubation time.•mcrA gene copies positively correlated with the reduction of Fe(III).