混合添加生物炭和Fe3O4的青稞秸秆厌氧消化产甲烷工艺及微生物功能优化

Optimization of anaerobic digestion process for methane production and microbial functions of hulless barley straw with mixed addition of biochar and Fe3O4

摘要:

目的 明确混合添加生物炭和Fe₃O₄介导的青稞秸秆厌氧消化产甲烷的最优工艺参数，并探究混合添加生物炭和Fe₃O₄在木质纤维素类废弃物厌氧消化应用中的可行性。方法 以青稞秸秆为原料，通过单因素试验和响应面法对混合添加生物炭和Fe₃O₄介导的青稞秸秆厌氧消化产甲烷工艺进行优化。利用宏基因组技术分析消化过程中的微生物群落结构和甲烷代谢途径。结果 经响应面模型验证试验得到最优工艺条件为：总固体含量6.32%、生物炭与Fe₃O₄混合比6.83:3.17、接种比(接种污泥与青稞秸秆挥发性固体量的比值) 2.51。在该条件下，基于挥发性固体计算的累积甲烷产量实测值为269.04 mL/g，与预测值(265.95 mL/g)的相对误差小于5%，验证了模型的有效性。该优化条件下的混合添加处理能显著提高青稞秸秆的产甲烷能力(P<0.05)，效果与化学预处理相当，同时提升了乙酸含量，并减少了丙酸和丁酸的积累。宏基因组分析显示，拟杆菌门未分类属(unclassified_Bacteroidota)、未分类细菌(unclassified_Bacteria)、梭菌属(Clostridium)、丝状杆菌属(Fibrobacter)等细菌类群，以及甲烷八叠球菌属(Methanosarcina)、甲烷丝菌属(Methanothrix)等乙酸营养型产甲烷菌的相对丰度增加，促进了乙酸的利用并强化了微生物间的种间直接电子传递(direct interspecies electron transfer, DIET)。甲烷代谢途径分析表明，混合添加生物炭和Fe₃O₄的消化系统强化了乙酸营养型产甲烷途径，从而提升了甲烷产量。结论 响应面法能较好地优化混合添加生物炭和Fe₃O₄介导的青稞秸秆厌氧消化产甲烷工艺。混合添加生物炭和Fe₃O₄是一种高效且环境友好的木质纤维素类废弃物处理方法，有助于提升生物甲烷的产量。

关键词:青稞秸秆;厌氧消化;生物炭;Fe₃O₄;响应面法;宏基因组;微生物群落;甲烷代谢途径

Abstract:

Objective To optimize the anaerobic digestion process for methane production of hulless barley straw with mixed addition of biochar and Fe₃O₄ and investigate the feasibility of mixed addition of biochar and Fe₃O₄ in the anaerobic digestion of lignocellulosic waste.Methods We employed single factor and response surface experiments to optimize the anaerobic digestion process for methane production of hulless barley straw with mixed addition of biochar and Fe₃O₄. Metagenomics was employed to analyze the microbial community structure and methane production pathway during digestion.Results The optimal digestion conditions were 6.32% total solids, biochar-to-Fe₃O₄ ratio of 6.83:3.17, and inoculation ratio (volatile solids ratio of inoculum to hulless barley straw) of 2.51. Under these conditions, the measured value of cumulative methane production based on volatile solids was 269.04 mL/g, with a relative error of less than 5% from the predicted value (265.95 mL/g), which indicated that the model was effective. The mixed addition treatment under the optimized conditions increased the methane production of hulless barley straw (P<0.05), with the effect comparable to that of the chemical pre-treatment. Meanwhile, the treatment increased the acetic acid content while reducing the accumulation of propionic and butyric acids. Metagenomic analysis showed increases in the relative abundance of bacterial taxa such as unclassified_Bacteroidota, unclassified_Bacteria, Clostridium, and Fibrobacter, as well as acetotrophic methanogens such as Methanosarcina and Methanothrix, which promoted the utilization of acetic acid and enhanced the direct interspecies electron transfer (DIET) between microorganisms. The mixed addition of biochar and Fe₃O₄ in the anaerobic digestion system enhanced the acetotrophic methanogenic pathway, thereby enhancing methane production.Conclusion The response surface methodology can optimize the anaerobic digestion process for methane production of hulless barley straw with mixed addition of biochar and Fe₃O₄. The mixed addition of biochar and Fe₃O₄ enables efficient production of biomethane and environmentally friendly treatment of lignocellulosic waste.

Key words:hulless barley straw;anaerobic digestion;biochar;Fe₃O₄;response surface methodology;metagenome;microbial community;methane production pathway