Biogas production by co-ensiling catch crops and straw, effect of substrate blend and microbial communities

The combination of catch crop (CC) and barley straw(S) for biogas production was investigated in order to evaluate the ensiling process in batch assay and in continuous process. Based on two new agriculture strategies designed to produce energy and improve nutrient cycling in organic farming are being evaluated, one of them consisting on the harvest of straw and catch crop in different periods whereas the other strategy consists on harvesting them at the same time. Catch crops is promoted to reduce nutrient leaching during rainy season and straw that is not used for animal feeding or bedding is generally left in the field. Mixtures of CC and S provides several advantages: 1) Provides adequate TS for silage, 2) Absorbs the silage effluent, 3) Produces high LAB activity, and 4) Provides an optimal C/N for anaerobic digestion (AD). The effect of feeding compositions (straw or manurea ddition) on the microbial community structures were also investigated

Comparative analysis of methanogenic communities in different laboratory-scale anaerobic digesters

© 2016 Ayrat M. Ziganshin et al.Comparative analysis of methanogenic archaea compositions and dynamics in 11 laboratory-scale continuous stirred tank reactors fed with different agricultural materials (chicken manure, cattle manure, maize straw, maize silage, distillers grains, and Jatropha press cake) was carried out by analysis of the methyl coenzyme-M reductase -subunit (mcrA) gene. Various taxa within Methanomicrobiales, Methanobacteriaceae, Methanosarcinaceae, Methanosaetaceae, and Methanomassiliicoccales were detected in the biogas reactors but in different proportions depending on the substrate type utilized as well as various process parameters. Improved coverage and higher taxonomic resolution of methanogens were obtained compared to a previous 16S rRNA gene based study of the same reactors. Some members of the genus Methanoculleus positively correlated with the relative methane content, whereas opposite correlations were found for Methanobacterium. Specific biogas production was found to be significantly correlating with Methanosarcinaceae. Statistical analysis also disclosed that some members of the genus Methanoculleus positively correlated with the ammonia level, whereas the prevalence of Methanocorpusculum, Methanobacterium, and Methanosaeta was negatively correlated with this parameter. These results suggest that the application of methanogenic archaea adapted to specific feedstock might enhance the anaerobic digestion of such waste materials in full-scale biogas reactors

Effects of the reduction of the hydraulic retention time to 1.5 days at constant organic loading in CSTR, ASBR, and fixed-bed reactors - Performance and methanogenic community composition

The hydraulic retention time (HRT) is one of the key parameters in biogas processes and often it is postulated that a minimum HRT of 10-25 days is obligatory in continuous stirred tank reactors (CSTR) to prevent a washout of slow growing methanogens. In this study the effects of the reduction of the HRT from 6 to 1.5 days on performance and methanogenic community composition in different systems with and without immobilization operated with simulated thin stillage (STS) at mesophilic conditions and constant organic loading rates (OLR) of 10gL-1d-1 of volatile solids were investigated. With the reduction of the HRT process instability was first observed in the anaerobic sequencing batch reactor (ASBR) (at HRT of 3 days) followed by the CSTR (at HRT of 2 days). The fixed bed reactor (FBR) was stable until the end of the experiment, but the reduction of the HRT to 1.5 days caused a decrease of the specific biogas production to about 450Lkg-1 of VS compared to about 600Lkg-1 of VS at HRTs of 4-5 days. Methanoculleus and Methanosarcina were the dominant genera under stable process conditions in the CSTR and the ASBR and members of Methanosaeta and Methanospirillum were only present at HRT of 4 days and lower. In the effluent of the FBR Methanosarcina spp. were not detected and Methanosaeta spp. were more abundant then in the other reactors. © 2014 Elsevier Ltd

Reduction of the hydraulic retention time at constant high organic loading rate to reach the microbial limits of anaerobic digestion in various reactor systems

© 2016 Elsevier LtdThe effects of hydraulic retention time (HRT) reduction at constant high organic loading rate on the activity of hydrogen-producing bacteria and methanogens were investigated in reactors digesting thin stillage. Stable isotope fingerprinting was additionally applied to assess methanogenic pathways. Based on hydA gene transcripts, Clostridiales was the most active hydrogen-producing order in continuous stirred tank reactor (CSTR), fixed-bed reactor (FBR) and anaerobic sequencing batch reactor (ASBR), but shorter HRT stimulated the activity of Spirochaetales. Further decreasing HRT diminished Spirochaetales activity in systems with biomass retention. Based on mcrA gene transcripts, Methanoculleus and Methanosarcina were the predominantly active in CSTR and ASBR, whereas Methanosaeta and Methanospirillum activity was more significant in stably performing FBR. Isotope values indicated the predominance of aceticlastic pathway in FBR. Interestingly, an increased activity of Methanosaeta was observed during shortening HRT in CSTR and ASBR despite high organic acids concentrations, what was supported by stable isotope data

Comparative analysis of methanogenic communities in different laboratory-scale anaerobic digesters

© 2016 Ayrat M. Ziganshin et al.Comparative analysis of methanogenic archaea compositions and dynamics in 11 laboratory-scale continuous stirred tank reactors fed with different agricultural materials (chicken manure, cattle manure, maize straw, maize silage, distillers grains, and Jatropha press cake) was carried out by analysis of the methyl coenzyme-M reductase -subunit (mcrA) gene. Various taxa within Methanomicrobiales, Methanobacteriaceae, Methanosarcinaceae, Methanosaetaceae, and Methanomassiliicoccales were detected in the biogas reactors but in different proportions depending on the substrate type utilized as well as various process parameters. Improved coverage and higher taxonomic resolution of methanogens were obtained compared to a previous 16S rRNA gene based study of the same reactors. Some members of the genus Methanoculleus positively correlated with the relative methane content, whereas opposite correlations were found for Methanobacterium. Specific biogas production was found to be significantly correlating with Methanosarcinaceae. Statistical analysis also disclosed that some members of the genus Methanoculleus positively correlated with the ammonia level, whereas the prevalence of Methanocorpusculum, Methanobacterium, and Methanosaeta was negatively correlated with this parameter. These results suggest that the application of methanogenic archaea adapted to specific feedstock might enhance the anaerobic digestion of such waste materials in full-scale biogas reactors

Isolation of hydrocarbonoclastic bacteria from bilge oil contaminated water

Two bacterial strains, i.e. Pseudomonas mendocina and Ochrobactrum sp. were isolated from bilge oil contaminated water of Mormugao harbour, Goa, India and grown in a culture medium with hexadecane as the sole carbon source. Pseudomonas mendocina was used in further studies as it was the dominant strain. This strain effectively degraded tetradecane, hexadecane and octadecane leaving a residual concentration of about 73 %, 54 % and 40 % respectively in 120 h. Sequence analysis of the dominant bands from the denaturing gradient gel electrophoresis profiles revealed the differences between the genera of bilge oil contaminated sea water and its enrichment culture on hexadecane indicating a shift in community structure based on the type of substrate available. Pseudomonas mendocina amplified for the following catabolic genes namely C23O, nid and ndo. Based on the catabolic gene study the potential of the bacterial strain isolated, i.e. Pseudomonas mendocina seems to be interesting as it will be able to degrade polyaromatic hydrocarbons as well. Physicochemical properties of Pseudomonas mendocina indicates production of exopolysaccharides based on the value of its isoelectric point

Comparative analysis of methanogenic communities in different laboratory-scale anaerobic digesters

© 2016 Ayrat M. Ziganshin et al.Comparative analysis of methanogenic archaea compositions and dynamics in 11 laboratory-scale continuous stirred tank reactors fed with different agricultural materials (chicken manure, cattle manure, maize straw, maize silage, distillers grains, and Jatropha press cake) was carried out by analysis of the methyl coenzyme-M reductase -subunit (mcrA) gene. Various taxa within Methanomicrobiales, Methanobacteriaceae, Methanosarcinaceae, Methanosaetaceae, and Methanomassiliicoccales were detected in the biogas reactors but in different proportions depending on the substrate type utilized as well as various process parameters. Improved coverage and higher taxonomic resolution of methanogens were obtained compared to a previous 16S rRNA gene based study of the same reactors. Some members of the genus Methanoculleus positively correlated with the relative methane content, whereas opposite correlations were found for Methanobacterium. Specific biogas production was found to be significantly correlating with Methanosarcinaceae. Statistical analysis also disclosed that some members of the genus Methanoculleus positively correlated with the ammonia level, whereas the prevalence of Methanocorpusculum, Methanobacterium, and Methanosaeta was negatively correlated with this parameter. These results suggest that the application of methanogenic archaea adapted to specific feedstock might enhance the anaerobic digestion of such waste materials in full-scale biogas reactors

Comparative analysis of methanogenic communities in different laboratory-scale anaerobic digesters

© 2016 Ayrat M. Ziganshin et al.Comparative analysis of methanogenic archaea compositions and dynamics in 11 laboratory-scale continuous stirred tank reactors fed with different agricultural materials (chicken manure, cattle manure, maize straw, maize silage, distillers grains, and Jatropha press cake) was carried out by analysis of the methyl coenzyme-M reductase -subunit (mcrA) gene. Various taxa within Methanomicrobiales, Methanobacteriaceae, Methanosarcinaceae, Methanosaetaceae, and Methanomassiliicoccales were detected in the biogas reactors but in different proportions depending on the substrate type utilized as well as various process parameters. Improved coverage and higher taxonomic resolution of methanogens were obtained compared to a previous 16S rRNA gene based study of the same reactors. Some members of the genus Methanoculleus positively correlated with the relative methane content, whereas opposite correlations were found for Methanobacterium. Specific biogas production was found to be significantly correlating with Methanosarcinaceae. Statistical analysis also disclosed that some members of the genus Methanoculleus positively correlated with the ammonia level, whereas the prevalence of Methanocorpusculum, Methanobacterium, and Methanosaeta was negatively correlated with this parameter. These results suggest that the application of methanogenic archaea adapted to specific feedstock might enhance the anaerobic digestion of such waste materials in full-scale biogas reactors

Characterization of wheat straw-degrading anaerobic alkali-tolerant mixed cultures from soda lake sediments by molecular and cultivation techniques

Alkaline pretreatment has the potential to enhance the anaerobic digestion of lignocellulosic biomass to biogas. However, the elevated pH of the substrate may require alkalitolerant microbial communities for an effective digestion. Three mixed anaerobic lignocellulolytic cultures were enriched from sediments from two soda lakes with wheat straw as substrate under alkaline (pH 9) mesophilic (37°C) and thermophilic (55°C) conditions. The gas production of the three cultures ceased after 4 to 5 weeks, and the produced gas was composed of carbon dioxide and methane. The main liquid intermediates were acetate and propionate. The physiological behavior of the cultures was stable even after several transfers. The enrichment process was also followed by molecular fingerprinting (terminal restriction fragment length polymorphism) of the bacterial 16S rRNA gene and of the mcrA/mrtA functional gene for methanogens. The main shift in the microbial community composition occurred between the sediment samples and the first enrichment, whereas the structure was stable in the following transfers. The bacterial communities mainly consisted of Sphingobacteriales, Clostridiales and Spirochaeta, but differed at genus level. Methanothermobacter and Methanosarcina genera and the order Methanomicrobiales were predominant methanogenes in the obtained cultures. Additionally, single cellulolytic microorganisms were isolated from enrichment cultures and identified as members of the alkaliphilic or alkalitolerant genera. The results show that anaerobic alkaline habitats harbor diverse microbial communities, which can degrade lignocellulose effectively and are therefore a potential resource for improving anaerobic digestion