Biochar facilitating methanogens evolution by enhancing extracellular electron transfer to boost anaerobic digestion of swine manure under ammonia stress - Raw data of bacteria

This study explored the mechanisms of biochar mitigating ammonia inhibition onanaerobic digestion (AD) of swine manure. 2-8g/L exogeneous ammonia dosagesgradually inhibited AD, which resulting in the efficiencies of hydrolysis, acidogenesisand methanogenesis declined by 3.4-70.8%, 6.0-82.0%, and 4.9-93.8%. Addingbiochar mitigated the inhibition, especially fulfilled methane production under 8g/Lexogenous ammonia addition. With biochar assistance, the microbial activities ofelectron transport system and extracellular electron transfer were enhanced, and themethanogen of Methanosarcina was primarily enriched. Meanwhile, biocharupregulated the genes encoding formylmethanofuran dehydrogenase andmethenyltetrahydromethanopterin cyclohydrolase for CO2-reducing methanogenesispathway by 26.9-40.8%. It was believed that biochar mediated direct interspecieselectron transfer between syntrophic partners to trigger methane production underammonia stress. Interestingly, as the acclimated microbial community established,removal biochar hardly depressed AD performances, addressing the key role ofbiochar for methanogen evolution to resist ammonia stress rather than anindispensable function when the evolution completed.

本研究探究了生物炭（biochar）缓解猪粪厌氧消化（anaerobic digestion, AD）中氨抑制效应的作用机制。2~8g/L的外源氨投加会逐步抑制AD过程，使得水解、产酸与产甲烷效率分别下降3.4%~70.8%、6.0%~82.0%与4.9%~93.8%。投加生物炭可有效缓解该抑制效应，尤其在8g/L外源氨条件下显著提升甲烷产率。在生物炭的辅助下，微生物的电子传递系统活性与胞外电子转移（extracellular electron transfer）能力得到增强，且甲烷八叠球菌（Methanosarcina）成为主要富集的产甲烷菌。同时，生物炭可将参与二氧化碳还原产甲烷途径的甲酰甲烷呋喃脱氢酶与亚甲基四氢甲烷蝶呤环水解酶的编码基因表达量上调26.9%~40.8%。研究表明，生物炭可介导互营伙伴间的种间直接电子转移（direct interspecies electron transfer），从而在氨胁迫条件下触发甲烷生成过程。值得注意的是，当驯化的微生物群落构建完成后，移除生物炭几乎不会降低AD运行性能，这提示生物炭在产甲烷菌演化以抵御氨胁迫的过程中发挥核心作用，而非在演化完成后成为不可或缺的功能组分。