Microflora communities which can convert digested sludge to biogas

In the present study, we developed several microflora communities that utilize digested sludge (DS), the recalcitrant waste product of anaerobic digestion, as a substrate for biogas production with the aim of their future application to DS recycling. Strict enrichment with DS as the sole nutrient source was introduced to culture microbes from soil and herbivore dung samples; microflora communities promoting stable levels of biogas production were obtained. The average methane and hydrogen yield from soil-derived microflora were 4.86 and 0.94 ml per 1.0 g DS, respectively. Notably, two microflora communities enriched from a riverbank sediment produced 20.79 ml and 14.10 ml methane from 1.0 g DS. By contrast, the methane and hydrogen yield for herbivore dung-derived microfloras were on average 1.31 ml and 1.87 ml per 1.0 g DS, respectively. Potent hydrogen-biogas producers were obtained from rabbit (4.12 ml per 1.0 g DS), goat (3.16 ml per 1.0 g DS), and sheep dung (2.52 ml per 1.0 g DS). The cultured microflora communities included representatives from the eubacterial genera, Clostridiaceae and Eubacteriaceae together with several anaerobic genera. Pseudomonas spp. are found in the riverbank sediment-derived microfloras, suggesting that the floras employ syntrophic acetate oxidation and hydrogentrophic methanogenesis (SAO-HM) pathway for methane production. The methanogenic microflora communities were dominated by bacteria from the Methanobacteriaceae family and unclassified archaea. Moreover, ascomycetous fungi and protists were found, implying that they act as oxygen scavengers and bacterial grazers, respectively. Enzymatic analysis suggested that the microfloras hydrolyze DS via cellulase, chitinase, and protease activities.

本研究构建了若干个菌群群落，以厌氧消化产生的难降解副产物消化污泥（digested sludge，以下简称DS）作为沼气生产的底物，旨在未来将其应用于DS的循环利用。本研究以DS作为唯一营养源开展严格富集培养，从土壤及草食动物粪便样本中分离培养微生物，最终获得了可稳定产出沼气的菌群群落。土壤来源菌群的甲烷与氢气产率均值分别为每1.0g DS产出4.86ml和0.94ml。值得注意的是，从河岸沉积物中富集得到的两个菌群群落，每1.0g DS可分别产出20.79ml和14.10ml甲烷。与之相比，草食动物粪便来源菌群的甲烷与氢气产率均值分别为每1.0g DS产出1.31ml和1.87ml。从兔（每1.0g DS产4.12ml）、山羊（每1.0g DS产3.16ml）及绵羊粪便中分离得到了高效产氢沼气菌群。所培养的菌群群落包含真细菌类群中的梭菌科（Clostridiaceae）、真杆菌科（Eubacteriaceae），以及多个厌氧属的代表菌种。河岸沉积物来源的菌群中检测到假单胞菌属（Pseudomonas spp.），表明该菌群通过互营乙酸氧化-氢营养型产甲烷（syntrophic acetate oxidation and hydrogentrophic methanogenesis，简称SAO-HM）途径实现甲烷生成。产甲烷菌群群落以产甲烷杆菌科（Methanobacteriaceae）细菌及未分类古菌为优势类群。此外，菌群中还检测到子囊菌（ascomycetous fungi）及原生生物（protists），分别推测其扮演氧清除剂与细菌捕食者的角色。酶学分析表明，该菌群通过纤维素酶、几丁质酶及蛋白酶的活性实现对DS的水解作用。