Happy marriage across the evolution: co-operation of methanogenic archaea and anaerobic fungi

Four anaerobic fungi (AF) strains, isolated from faeces of anoa, giraffe, bison and moose, were assessed for their ability to degrade lignocellulosic biomass. The effects on biogas production of anaerobic fungi from these animal species were determined in two step batch experiments. The hydrolysis process during the AF incubation led to an initial increase of biogas production, an accelerated degradation of dry matter and an increased concentration of volatile fatty acids. Thus, a separate hydrolytic pre-treatment phase with anaerobic fungi, represents a feasible strategy to improve biogas production from lignocellulosic substrates

Improving methane production from lignocellulosic biomass pre-treated with anaerobic fungi

Two anaerobic fungi (AF) strains, isolated from faeces of an elephant and of a sheep, were assessed for their ability to degrade lignocellulosic biomass. The effects on biogas production of anaerobic fungi from both animal species were determined in two step batch experiments. The hydrolysis process during the AF incubation led to an initial increase of biogas production, an accelerated degradation of dry matter and an increased concentration of volatile fatty acids. Thus, a separate hydrolytic pre-treatment phase with anaerobic fungi, represents a feasible strategy to improve biogas production from lignocellulosic substrates

The Planktonic Core Microbiome and Core Functions in the Cattle Rumen by Next Generation Sequencing

The cow rumen harbors a great variety of diverse microbes, which form a complex, organized community. Understanding the behavior of this multifarious network is crucial in improving ruminant nutrient use efficiency. The aim of this study was to expand our knowledge by examining 10 Holstein dairy cow rumen fluid fraction whole metagenome and transcriptome datasets. DNA and mRNA sequence data, generated by Ion Torrent, was subjected to quality control and filtering before analysis for core elements. The taxonomic core microbiome consisted of 48 genera belonging to Bacteria (47) and Archaea (1). The genus Prevotella predominated the planktonic core community. Core functional groups were identified using co-occurrence analysis and resulted in 587 genes, from which 62 could be assigned to metabolic functions. Although this was a minimal functional core, it revealed key enzymes participating in various metabolic processes. A diverse and rich collection of enzymes involved in carbohydrate metabolism and other functions were identified. Transcripts coding for enzymes active in methanogenesis made up 1% of the core functions. The genera associated with the core enzyme functions were also identified. Linking genera to functions showed that the main metabolic pathways are primarily provided by Bacteria and several genera may serve as a “back-up” team for the central functions. The key actors in most essential metabolic routes belong to the genus Prevotella. Confirming earlier studies, the genus Methanobrevibacter carries out the overwhelming majority of rumen methanogenesis and therefore methane emission mitigation seems conceivable via targeting the hydrogenotrophic methanogenesis

Analyses of the Large Subunit Histidine-Rich Motif Expose an Alternative Proton Transfer Pathway in [NiFe] Hydrogenases

A highly conserved histidine-rich region with unknown function was recognized in the large subunit of [NiFe] hydrogenases. The HxHxxHxxHxH sequence occurs in most membrane-bound hydrogenases, but only two of these histidines are present in the cytoplasmic ones. Site-directed mutagenesis of the His-rich region of the T. roseopersicina membrane-attached Hyn hydrogenase disclosed that the enzyme activity was significantly affected only by the replacement of the His104 residue. Computational analysis of the hydrogen bond network in the large subunits indicated that the second histidine of this motif might be a component of a proton transfer pathway including Arg487, Asp103, His104 and Glu436. Substitutions of the conserved amino acids of the presumed transfer route impaired the activity of the Hyn hydrogenase. Western hybridization was applied to demonstrate that the cellular level of the mutant hydrogenases was similar to that of the wild type. Mostly based on theoretical modeling, few proton transfer pathways have already been suggested for [NiFe] hydrogenases. Our results propose an alternative route for proton transfer between the [NiFe] active center and the surface of the protein. A novel feature of this model is that this proton pathway is located on the opposite side of the large subunit relative to the position of the small subunit. This is the first study presenting a systematic analysis of an in silico predicted proton translocation pathway in [NiFe] hydrogenases by site-directed mutagenesis

Use of Ensiled Green Willow Biomass in Biogas Fermentation

The biggest challenges of our era include climate change and the global fossil energy problem. Extensive utilization of renewable energy sources should be a part of the solution for both these problems. Biogas is a versatile renewable energy carrier that has the potential to substitute fossil fuels. The most frequently utilized substrates for the anaerobic digestion (AD) process include maize silage today, but there is an increasing demand for second-generation biomass sources, which are cheaper and do not interfere with the cultivation of food production. Green biomass from short rotation coppice willow (GWB) may be a promising alternative. However, to ensure feedstock quantity and quality all year round, a preservation method has to be developed. We attempted to ensilage the biomass and subsequently utilized the resulting willow-silage in batch fermenters. Various mixtures of lactic acid bacteria were employed to facilitate ensiling by inoculation of the substrate in anaerobic jars for 60 days. During the ensiling analytical investigations, (HPLC, pH, oTS/TS%) were carried out in order to follow the build-up of fermentation products. AD fermentations were assembled from the ensilaged biomass and the methane production was measured for 56 days. The total methane yields of the ensilaged biomass were 8–15% higher than that of the fresh biomass and methane production rates were also improved. Our fndings suggest that ensiling is not only an excellent preservation method for willow biomass, but also stimulates its AD