磁性生物炭基材料对厌氧消化微生物种间电子传递的促进效应机制研究

The rate of interspecies electron transfer is essential for maintaining the metabolic balance among synthrophic microbial communities and enhancing the performance of anaerobic digestion. Both biochar and nano-magnetic materials can promote methanogenesis by stimulating direct interspecies electron transfer. In practical applications, biochar is easy to float on the surface of digester and increase the resistance during mass transfer; nano-magnetic materials possibly are toxic to microorganisms under long time effects and risky for ecology. This project is planned to prepare magnetic biochar-based composites to overcome the individual disadvantages of abovementioned two materials. Through the long-term operation of anaerobic reactors fed with wheat straw, the effects of magnetic biocar-based composites on anaerobic digestion of complex organic waste will be evaluated. Combining the application of methanogenesis inhibitor, stable isotope tracer, thermodynamic calculations, and current density measurement, the carbon flow and electron flow in the process of magnetic biochar-based composites-mediated anaerobic digestion will be analyzed quantitatively. Stimulating effects of the composites could be assessed step by step on the interspecies electron transfer. Based on the technology of electrochemical analysis, in situ fourier transform infrared spectroscopy, three-dimensional excitation-emission matrix spectroscopy, fluorescence in situ hybridization and high-throughput pyrosequencing, the functional structure and catalytic activity of microbial endogenous redox mediators and the structure and temporal-special distribution of microbial populations are to be investigated. Finally, the microbial mechanism of magnetic biochar-based composites promoting methanogenesis is expected to be revealed. The final aim of this project is to provide technical support and theoretical guidance for improving the performance of anaerobic digestion process.

微生物种间电子传递效率对维持菌群间互营共生代谢平衡、提升厌氧消化工艺效能至关重要。生物炭和纳米磁性物均能促进种间电子直接传递。然而，在实际应用中，生物炭易漂浮、增加传质阻力；纳米磁性物会毒害微生物、有生态风险。本项目拟通过制备磁性生物炭基材料，克服两种材料各自的弊端。以小麦秸秆为底物进行长期厌氧消化，评价磁性生物炭基材料对复杂有机物厌氧消化的长期促进性能；结合产甲烷微生物抑制剂、稳定同位素标记、热力学计算、电流密度测定等技术方法对磁性生物炭基材料介导的厌氧消化过程碳流和电子流进行量化分析；逐级评价其对厌氧消化微生物种间电子传递的促进效应。借助电化学分析、原位红外光谱分析、三维荧光光谱分析、荧光原位杂交及高通量测序技术等对微生物内生氧还介体物官能结构特征与活性、微生物种群结构与时空分布进行探究，阐明磁性生物炭基材料介导的厌氧消化微生物学机制，以期为厌氧消化工艺效能提升提供技术支撑和理论指导。

微生物种间电子传递效率对维持菌群间互营共生代谢平衡、提升厌氧消化工艺效能至关重要。生物炭和纳米磁性物均能促进种间电子直接传递。然而，在实际应用中，生物炭易漂浮、增加传质阻力；纳米磁性物会毒害微生物、有生态风险。基于此，我们制备了不同类型的磁性生物炭基材料，通过小麦秸秆单次批式厌氧消化、传代批式厌氧消化和半连续厌氧消化试验，采用X射线光电子能谱分析、16S rRNA基因高通量测序等技术探明磁性生物炭基材料理化性质特征并进行性能优化，揭示磁性生物炭对复杂有机物厌氧消化的长期促进效应及其对微生物种间电子传递的促进效应，阐明磁性生物炭基材料介导的厌氧消化微生物学机制，以期为厌氧消化工艺效能提升提供技术策略和数据支撑。结果表明:（1）浸渍-一步炭化法可以获得具有稳定性能的磁性生物炭基材料，硝酸铁溶液浸渍优于硫酸铁和氯化铁，铁离子浓度是关键因素，过高的铁离子浓度会弱化其性能，额外引入Fe2+不能使磁性生物炭的理化性能更优越；（2）高有机负荷单次批式厌氧消化下，不同类型生物炭均能缓解中间产物累积产生的抑制效应，缩短产气停滞期，并提升最终累计产气率，中温热解炭能最大程度缩短停滞期，而水热炭对累计甲烷产率的提升最高，水热炭和铁磁性材料的协同促进效应最明显；（3）在传代批次厌氧消化中，磁性生物炭基材料添加对产气性能的促进效能与有机负荷率有关，并随发酵批次变化。原生生物炭在短效促进产气性能方面表现优越，而磁性生物炭在长期的厌氧发酵过程中，其促进效应更明显，生物炭材料能选择性富集特定细菌群落，强化微生物种间互养共生电子传递，而磁性生物炭基材料添加更有利于古菌群落结构较高的均匀性和产甲烷途径的多样性，从而维持较高的甲烷百分含量；（4）在半连续厌氧消化中，生物炭添加联合低负荷混合原料启动和消化液回流可提高系统耐负荷冲击能力，维持更为稳定的产气率和高甲烷含量，实现半连续厌氧消化反应器的高效稳定运行。