Comparative and Joint Analysis of Two Metagenomic Datasets from a Biogas Fermenter Obtained by 454-Pyrosequencing

Biogas production from renewable resources is attracting increased attention as an alternative energy source due to the limited availability of traditional fossil fuels. Many countries are promoting the use of alternative energy sources for sustainable energy production. In this study, a metagenome from a production-scale biogas fermenter was analysed employing Roche's GS FLX Titanium technology and compared to a previous dataset obtained from the same community DNA sample that was sequenced on the GS FLX platform. Taxonomic profiling based on 16S rRNA-specific sequences and an Environmental Gene Tag (EGT) analysis employing CARMA demonstrated that both approaches benefit from the longer read lengths obtained on the Titanium platform. Results confirmed Clostridia as the most prevalent taxonomic class, whereas species of the order Methanomicrobiales are dominant among methanogenic Archaea. However, the analyses also identified additional taxa that were missed by the previous study, including members of the genera Streptococcus, Acetivibrio, Garciella, Tissierella, and Gelria, which might also play a role in the fermentation process leading to the formation of methane. Taking advantage of the CARMA feature to correlate taxonomic information of sequences with their assigned functions, it appeared that Firmicutes, followed by Bacteroidetes and Proteobacteria, dominate within the functional context of polysaccharide degradation whereas Methanomicrobiales represent the most abundant taxonomic group responsible for methane production. Clostridia is the most important class involved in the reductive CoA pathway (Wood-Ljungdahl pathway) that is characteristic for acetogenesis. Based on binning of 16S rRNA-specific sequences allocated to the dominant genus Methanoculleus, it could be shown that this genus is represented by several different species. Phylogenetic analysis of these sequences placed them in close proximity to the hydrogenotrophic methanogen Methanoculleus bourgensis. While rarefaction analyses still indicate incomplete coverage, examination of the GS FLX Titanium dataset resulted in the identification of additional genera and functional elements, providing a far more complete coverage of the community involved in anaerobic fermentative pathways leading to methane formation

Comparative biochemical analysis during the anaerobic digestion of lignocellulosic biomass from six morphological parts of Williams Cavendish banana (Triploid Musa AAA group) plants

We studied banana lignocellulosic biomass (BALICEBIOM) that is abandoned after fruit harvesting, and assessed its biochemical methane potential, because of its potential as an energy source. We monitored biogas production from six morphological parts (MPs) of the "Williams Cavendish" banana cultivar using a modified operating procedure (KOP) using KOH. Volatile fatty acid (VFA) production was measured using high performance liquid chromatography. The bulbs, leaf sheaths, petioles-midribs, leaf blades, rachis stems, and floral stalks gave total biogas production of 256, 205, 198, 126, 253, and 221 ml g-1 dry matter, respectively, and total biomethane production of 150, 141, 127, 98, 162, and 144 ml g-1, respectively. The biogas production rates and yields depended on the biochemical composition of the BALICEBIOM and the ability of anaerobic microbes to access fermentable substrates. There were no significant differences between the biogas analysis results produced using KOP and gas chromatography. Acetate was the major VFA in all the MP sample culture media. The bioconversion yields for each MP were below 50 %, showing that these substrates were not fully biodegraded after 188 days. The estimated electricity that could be produced from biogas combustion after fermenting all of the BALICEBIOM produced annually by the Cameroon Development Corporation-Del Monte plantations for 188 days is approximately 10.5 × 106 kW h (which would be worth 0.80-1.58 million euros in the current market). This bioenergy could serve the requirements of about 42,000 people in the region, although CH4 productivity could be improved. © 2013 Springer Science+Business Media Dordrecht