Abstract
BackgroundA solid-state anaerobic digestion method is used to produce biogas from various solid wastes in China but the efficiency of methane production requires constant improvement. The diversity and abundance of relevant microorganisms play important roles in methanogenesis of biomass. The next-generation high-throughput pyrosequencing platform (Roche/454 GS FLX Titanium) provides a powerful tool for the discovery of novel microbes within the biogas-generating microbial communities.ResultsTo improve the power of our metagenomic analysis, we first evaluated five different protocols for extracting total DNA from biogas-producing mesophilic solid-state fermentation materials and then chose two high-quality protocols for a full-scale analysis. The characterization of both sequencing reads and assembled contigs revealed that the most prevalent microbes of the fermentation materials are derived from Clostridiales (Firmicutes), which contribute to degrading both protein and cellulose. Other important bacterial species for decomposing fat and carbohydrate are Bacilli, Gammaproteobacteria, and Bacteroidetes (belonging to Firmicutes, Proteobacteria, and Bacteroidetes, respectively). The dominant bacterial species are from six genera: Clostridium, Aminobacterium, Psychrobacter, Anaerococcus, Syntrophomonas, and Bacteroides. Among them, abundant Psychrobacter species, which produce low temperature-adaptive lipases, and Anaerococcus species, which have weak fermentation capabilities, were identified for the first time in biogas fermentation. Archaea, represented by genera Methanosarcina, Methanosaeta and Methanoculleus of Euryarchaeota, constitute only a small fraction of the entire microbial community. The most abundant archaeal species include Methanosarcina barkeri fusaro, Methanoculleus marisnigri JR1, and Methanosaeta theromphila, and all are involved in both acetotrophic and hydrogenotrophic methanogenesis.ConclusionsThe identification of new bacterial genera and species involved in biogas production provides insights into novel designs of solid-state fermentation under mesophilic or low-temperature conditions.
Highlights
A solid-state anaerobic digestion method is used to produce biogas from various solid wastes in China but the efficiency of methane production requires constant improvement
In order to find a better protocol for the isolation of high-quality DNA preparations for pyrosequencing, we set out to evaluate five DNA extraction methods
Using electrophoresis assay for checking quality and yield of genomic DNA extracts (Figure 1 and Table 1), we found that Protocols E, EY, and F gave rise to the highest yields, ranging from ~160.5 ng/μl to ~121.4 ng/μl, while Protocol P produced the lowest yield, with ~20.5 ng/μl
Summary
A solid-state anaerobic digestion method is used to produce biogas from various solid wastes in China but the efficiency of methane production requires constant improvement. The production of biogas through biomass fermentation, regarded as an environment-friendly, clean, and renewable resource, has been gaining more attention in many developed and developing countries [1,2]. The utilization of anaerobic fermentation to convert SW into biogas represents a promising effort if it can be accomplished at an industrial scale and in an economical way. The yield of methane, the major end-product of this process, has not been sufficient for an industrial-scale promotion, let alone economical plausibility
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