玉米秸秆固态和液态厌氧发酵产气性能与微生物种类比较研究

厌氧发酵产沼气是中国绿色农业发展过程处理农业废弃物的重要手段,该文以玉米秸秆为研究对象,开展液态、固态厌氧发酵产气性能、微生物系统多样性及演替规律的比较研究,得出如下结论:固态发酵总固体(TS)产气率及甲烷转化率略低于液态发酵,发酵结束后,前者沼液中N、P、C的含量要低于后者;乙酸是两发酵体系挥发性脂肪酸(VFAs)的主要组成,占总VFAs的70%以上。高通量测序结果发现,2个发酵系统中细菌主要以Bacteroidetes、Firmicutes、Proteobacteria、Cloacimonetes、Synergistetes及Verrucomicrobia为主,这6类菌群占总克隆数的80%以上。而Methanosaeta,Methanospirillum,Methanocorpusculum以及Methanoculleus是两系统优势古菌,并且随消化过程的进行,古菌群落呈现由乙酸型向氢营养型转变的趋势。发酵结束后,上述2类古菌在群落中的占比基本持平。对微生物多样性的聚类分析结果显示,在发酵第4天和第8天后,2个系统中细菌与古菌群落结构的差异逐渐明显。进一步分析表明,影响玉米秸秆液态发酵微生态结构的主要环境因子为乙酸,秸秆纤维素水解可能是制约物能转化率的关键过程;总磷(TP)是影响固态发酵系统微生态结构的关键环境因子,而如何增加产甲烷古菌的生物量是提高原料产气率的关键。该研究结果为调控玉米秸秆厌氧发酵过程、提高其生物降解效率提供了科学依据。

Comparison of biogas production and microbial species of corn straw in solid-state anaerobic digestion (SS-AD) and liquid anaerobic digestion (L-AD)

Anaerobic digestion(AD)is an important method to dispose agricultural waste in the process of green agriculture development in China.It not only solve the problem of fuel shortages in rural areas,but also realize the harmless treatment and multi-level resource utilization of waste.Based on the total solids(TS)content of the feedstock,AD has been developed as liquid anaerobic digestion(TS<15%)and solid-state anaerobic digestion(TS≥15%)technologies.In this paper,the gas production performance and micro-ecological succession law of corn straw in liquid and solid biogas fermentation were compared.The result showed that:The peak period of SS-AD biogas production was about 4 days later than that of L-AD,and the CH4 volume fraction of the SS-AD was lower than that of the L-AD in stable biogas production period.The biogas production rate of TS and methane conversion rate in SS-AD system were slightly lower than that of L-AD.After the fermentation,the contents of N,P and C in the SS-AD biogas slurry were lower than that of the L-AD.Acetic acid is the main component of VFAs in the two digestion systems,accounting for more than 70% of the total VFAs.High-throughput sequencing results showed that the bacteria in the two disgestion systems were mainly composed of Bacteroidetes,Firmicutes,Proteobacteria,Cloacimonetes,Synergistetes and Verrucomicrobia,which accounted for more than 80% of the total number of clones.Bacteroidetes is the largest class of bacteria,and its relative abundance is stable throughout the digestive stage,but the relative abundances of Proteobacteria and Firmicutes were decreased gradually after the start of fermentation,and eventually stabilized around 10%.The relative abundance of Cloacimonetes increases with digestion time,and the maximum value can reach 20.1%in SS-AD systems.The sum of the relative abundances of Verrucomicrobia and Synergistetes increases with the anaerobic digestion process.Methanosaeta,Methanospirillum,Methanocorpusculum and Methanoculleus are the dominant archaea in the two fermentation systems.These four types of archaea accounted for 24.4%-39.6% of the total number of clones in SS-AD system and 27.9%-48.0% in L-AD system.With the progress of the digestion,the archaea community showed a trend of transition from acetic acid nutrition to hydrogen nutrition.After fermentation,the proportion of these two types of archaea in the community wasin balance.The results of cluster analysis on microbial diversity showed that the difference between the bacteria and archaea community structure of the two systems gradually became obvious after the 4th and 8th day of fermentation.Further analysis showed that the main environmental factor affecting the L-AD micro-ecological structure of corn straw is acetic acid,and the hydrolysis of straw cellulose may be the key process to limit the conversion rate of raw materials.Phosphorus is the most important environmental factor affecting the micro-ecological structure of SS-AD systems,and how to increase the biomass of methanogenic archaea is the key to raise the biogas production rate of raw materials.The results of this study provide a scientific basis for regulating the anaerobic digestion process of corn straw and improving its bio-degradation efficiency.