微藻-真菌共生体高效同步生物净化沼液沼气的共生与作用机制研究

Developing strategies for algal-fungal symbiotic system is a new approach to realize utilization as resources for biogas slurry and to upgrade biogas, which have received considerable attention in recent years. One limitation of biogas production through single microalgae is that the amount of nutrients and CO2 in the digestate or crude biogas is insignificantly reduced and microalgae difficult to harvest after use. It is very necessary to make further research for symbiosis and synergy between crude biogas and biogas slurry biological elimination in the high efficient photo-bioreactor in order to keep sustainable biogas production. This research may use biogas slurry as the culture medium of algal-fungal symbiont growth and CO2 in the biogas or decomposition of fungi as carbon source. The reflux circulating photo-bioreactor utilized in this study could effectively upgrade biogas and simultaneously reduce nutrients content by growth of algal-fungal symbiont. This study focused on the performance of biogas upgrading and biogas slurry purification using combination of microalgae (Chlorella sp., Scenedesmus obliquus and Nitzschia palea) and fungus(Ganoderma lucidum) in the photo-bioreactor. Through the research of the mutual ecological effects of Ganoderma lucidum and dominant microalgae and the response of microalgae to quorum sensing signal molecules, and quantitative relationship of carbon source of the crude biogas and nutrients in the biogas slurry, and effect relationship of crude biogas’s and biogas slurry’s characteristics on biogas upgrading and biogas slurry treatment, and influence of biogas flow rate and dilution of biogas slurry on treatment effects, and finally illustrate synergistic effect between algal-fungal symbiont microalgae based biogas CO2 assimilation and biogas slurry nutrients removal. This research could further clearly defined the mutual action rule of microalgae and fungus, and finally provide scientific and theoretical base for development of comprehensive utilization of solid waste. So explore how to set up an effective photo-bioreactor system, not only have the theory innovation value, but also have the technological accumulation meaning.

藻菌共生体是解决单一微藻处理固废厌氧发酵沼液污染物去除率低，藻类回收利用困难，沼气品位低下等问题的一种新途径，已引起有关研究者高度重视。本研究以沼液为藻菌体生长基质，粗沼气中CO2和菌类分解产生的CO2为藻类生长碳源，藻类光合作用产生的氧气促进菌类的代谢活动，实现沼液沼气的同步生物净化。选用前期筛选出的优势微藻（小球藻、栅藻和谷皮菱形藻等）和真菌（灵芝菌）形成稳定的藻菌共生体，构建高效的光生物反应器处理系统。通过研究优势微藻与真菌间相互作用及其对真菌群体感应信号分子的响应；沼气和沼液营养基质间的数量关系；沼气沼液组分与净化效果之间的效应关系；沼气流量、沼液稀释对处理效果的影响，阐明藻菌共生体的共生机制及其长特性与沼液沼气特性的相互作用机制。本项目的开展，将进一步明确微藻与共生真菌间相互作用规律，为固废高效资源化循环利用提供科学的理论依据和技术积累。

本项目针对沼气中CH4品位偏低、沼液污染严重，常规微藻单一化培养难以采收的问题，驯化前期筛选出的优势微藻，使其藻种具有快速适应高浓度CO2环境的遗传学特性，驯化已筛选出的真菌菌种，使其对高浓度有机废水具有高度耐性，筛选得到小球藻（Chlorella vulgaris）、斜生栅藻（Scenedesmus obliquus）、羊角月牙藻（Selenastrum capricornutum）等3种优势藻种，并且与灵芝菌和活性污泥进行成球，在适宜培养条件下，形成藻菌共生体，应用于沼液和沼气的同步净化。通过外源添加不同浓度的独脚金内酯的类似物GR24 (0、10−11、10−9、10−7、10−6 M)，分析其对微藻生物量、叶绿素a含量、光合性能、胞内碳酸酐酶活性以及COD、TN、TP和CO2去除效率的影响。结果表明10-7 M GR24处理的藻生长速率和平均日产量分别为0.187±0.06 d−1和0.097±0.008 gL−1d−1。叶绿素荧光瞬态法结果表明，适量的GR24能增强微藻的光合性能。添加10-7 M GR24可以获得最大化学需氧量、总氮和二氧化碳去除率分别为78.62±2.36%、76.47±1.53%和64.05±1.15%，而10-9M的总磷去除率最高(80.27±1.93%)，确定GR24的最佳浓度范围为10-9 ~ 10-7 M。通过优化小球藻与灵芝菌共培养和成球化，实现了沼液中养分的完全去除以及沼气提纯。在摇床转速为160 rpm、菌藻比为1:10的条件下，在初始菌浓度为1.0×106孢子L−1的条件下，获得了最优菌藻共生体。沼液比例为3:7的混合培养最适合成球，得到的藻菌球直径约为3-4mm。红蓝混合波长为5:5时对COD、TN、TP和CO2的去除率最高。通过研制新型光生物反应器处理系统实现废弃物资源化循环利用目标，以光能为输入，生物质能高品质沼气为输出，实现了光能从藻类到高品质沼气的能量流动和C、N、P等营养元素的物质循环。沼气通过光生物反应器的净化效果显著，沼气中甲烷浓度从约40%上升到约90%；同时也显著消减了沼液的污染效应，实现了藻菌共生体的生物净化功能，获得更高的能源效率，进一步提升了沼液和沼气的同步净化效果。上述研究为微藻及藻菌共生体应用于同步沼气品位提升和沼液处理提供了重要参考，系统解析了沼气品位提升机理。