Hybrid read-based and genome-centric investigation of laboratory scale anaerobic digestion using various second and third generation substrates

Biogas production from co-digestion of second and third generation substrates is a promising alternative to replace similar complex polysaccharide containing first generation biomasses. In the present study energy willow (EW), simple water pre-treated chicken manure (TCM) and mixed microalgal-bacterial (MABA) biomass cultivated on wastewater by-product of chicken manure treatment were used. The BMP tests showed that biogas production of co-digestion was ~21% higher compared to the production using EW alone indicating a synergistic effect of co-substrates. During the AD in semi-CSTR, a slow but balanced operation was observed due to the optimized C/N ratio. In order to gain insights into the complex anaerobic decomposing microbiome and its functional network hybrid read-based and genome-centric metagenomics were employed. This hybrid investigation revealed that the major bacterial participants were the representatives of Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes phyla, while Methanomicrobia and Methanobacteria represented the archaeal constituents of the specific biodegrading community. Several CAZymes were found indicating active complex polysaccharide degradation processes. The bacterial phyla were shown to perform the long chain carbohydrate hydrolysis while methanogenesis were linked to the slow growing members of the complex community. It was concluded that an optimized balance between H2 producers and consumers was critical for the efficient and stable operation of the biogas microbial community utilizing second and third generation feedstock.

利用第二代与第三代底物进行共厌氧消化以生产沼气，是替代含复杂多糖的第一代生物质的极具前景的方案。本研究选用了能源柳（EW）、经简易水预处理的鸡粪（TCM），以及以鸡粪处理废水副产物培养得到的混合微藻-细菌（MABA）生物质。生物甲烷潜力（BMP）测试结果显示，共厌氧消化的沼气产量较单独使用能源柳时提升约21%，表明共底物间存在协同效应。在半连续搅拌槽式反应器（semi-CSTR）的厌氧消化过程中，由于碳氮比（C/N）得到优化，系统运行平稳且速率适中。为解析复杂的厌氧分解微生物组及其功能网络，本研究采用了基于测序读段与基因组聚焦的混合宏基因组学技术。该混合分析揭示，群落中的主要细菌类群隶属于厚壁菌门（Firmicutes）、放线菌门（Actinobacteria）、变形菌门（Proteobacteria）与拟杆菌门（Bacteroidetes），而古菌类群则以甲烷微菌纲（Methanomicrobia）和甲烷杆菌纲（Methanobacteria）为代表。研究检测到多种碳水化合物活性酶（CAZymes），表明复杂多糖的降解过程较为活跃。细菌类群负责长链碳水化合物的水解作用，而产甲烷过程则与群落中生长缓慢的成员相关。最终研究结论表明，产氢菌与产氢利用菌之间的优化平衡，对于利用第二代与第三代原料的沼气微生物群落实现高效稳定运行至关重要。