微好氧强化纤维类废弃物厌氧消化过程及机理研究

Anaerobic digestion technology is one of the most important methods during the disposal of cellulosic waste. However, due to the compact structure of the cellulosic substrate, some problems (e.g. low biogas production efficiency, long fermentation period) excited during the anaerobic digestion of cellulosic substrate. In view of the above problems, micro-aeration will be studied in this proposal to enhance the anaerobic digestion performance of cellulosic waste. Micro-aeration means introduction of limited oxygen into the anaerobic digestion system thus regulates the physiological and biochemical process of anaerobic digestion and enhances the anaerobic digestion efficiency finally. Preliminary researches of the applicant showed anaerobic digestion performance of cellulosic waste could be enhanced by micro-aeration. However, the mechanisms of micro-aeration are still unclear. In this proposal, GC-MS and isotope tracer technique will be applied to analyze the utilization approach of oxygen during micro-aeration. Various chemistry and spectrum technologies will be used to study the degradation characteristics of substrate and intermediate products. In addition, the succession of microbial community, key enzymes and functional genomes during micro-aeration will also be studied based on various molecular techniques. The mechanisms of how micro-aeration improving the anaerobic digestion efficiency will be analyzed based on the comprehensive analysis of the obtained data using multivariate statistical analysis software. The implementation of this proposal will contribute to the enrichment of anaerobic digestion theory, which would also provide technical reserves and references for the resource utilization of cellulosic waste.

厌氧消化技术是纤维类废弃物合理处置的重要手段之一。然而，由于纤维类废弃物的结构致密，导致其厌氧消化过程存在发酵周期长、产气效率低的问题。本项目针对以上问题提出微好氧强化纤维类废弃物厌氧消化过程的策略，即通过对厌氧消化体系引入适量的氧气，调控其生理生化过程，从而达到强化厌氧消化过程的目的。申请人初步试验结果表明微好氧能够强化纤维类废弃物厌氧消化过程，但其作用机理尚不清楚。本项目拟采用GC-MS和同位素示踪技术揭示微好氧过程中氧气的利用途径；结合多种化学、光谱学手段研究微好氧条件下底物降解规律及中间产物；借助多种分子生物学技术明确微好氧强化过程中的功能微生物、功能基因组和关键酶。并最终使用多元统计分析软件综合分析以上数据，解析微好氧强化纤维类废弃物厌氧消化过程的机理。本项目的实施能够丰富厌氧消化理论，对纤维类废弃物的资源化利用具有一定的理论与现实意义。

纤维类废弃物结构致密，其厌氧消化处理存在发酵周期长、产气效率低的问题。针对此，本研究开展了微好氧强化纤维类废弃物厌氧消化的研究并对其机理进行了探索。本项目已按计划完成了研究内容，达到了项目计划书中设定的研究目标，并根据试验进行增加了部分研究内容。最终开发出了微好氧强化纤维类废弃物厌氧消化的技术手段，阐明了相关机理。项目执行期内，发表SCI论文6篇，申请专利7项，培养硕士研究生4名，博士研究生1名。本项目取得的主要研究结果如下：微好氧在强化纤维类废弃物厌氧消化过程中低促高抑，在氧气负荷为0.2 mL/(g·VS·day)时玉米秸秆厌氧消化甲烷产量可达262.0 ± 6.0 mL/(g·VS)，相对于对照组提高了7.8%；微好氧条件下，与底物水解酸化相关的细菌如Firmicutes, Synergistota, Spirochaetota相对丰度明显提高，从而导致体系纤维素酶等水解酶类浓度的提高，并最终提高了底物的降解效率：微好氧条件下，玉米秸秆厌氧消化过程中纤维素、半纤维素、木质素的降解率分别可达68.23± 2.01%、73.10% ± 2.01%、26.85 ± 1.20%，相对于对照组分别提高了9.24%、4.01%、62.92%；同时，微好氧条件下对氧气具有一定耐受性的产甲烷菌如Methanobacterium相对丰度也明显提高，从而保证了体系产甲烷的正常进行：微好氧条件下，乙酸营养型产甲烷活性提高了5.2-32.6%，氢营养型产甲烷活性提高了3.4-6.7%；进一步的，本研究中报道了微好氧条件下，体系腐殖酸类物质浓度相对于对照组提高了27.48%，再加上体系与种间直接电子传递相关微生物丰度的提升，从而促进了互养产甲烷过程；同时，耦合微好氧氢气发酵和厌氧甲烷发酵可以减轻氧气对产甲烷菌的抑制作用，从而进一步提高微好氧的强化效果，当微好氧氧气负荷为10 mL/g VS时，玉米秸秆厌两相厌氧消化的能量回收率达到最大为10.6 kJ/g VS，相较于单项发酵提高了18%。上述结果，为纤维类废弃物高效厌氧消化系统的构建提供了参考，进一步丰富了厌氧消化相关的理论，对有机废弃物的高效资源化利用具有明显的理论及实际意义。