Construction of biogas metabolic pathway in a low‐temperature biogas fermentation system

Abstract

The main objective of this study was to establish the metabolic pathway of a biogas fermentation system active at low temperature, and to describe the bacterial and archaeal methanogenic species responsible. A biogas fermentation inoculum adapted to be active at 9°C was used in a 10‐L batch‐type temperature‐controlled fermentor, using pig manure as the raw material. Fermentation at 9°C was followed for 120 days. A combination of nonbiological and biological factors was analyzed. Species were identified from OTU analysis based on 16S rDNA amplicon sequencing, and correlation analysis was used to study the effect of nonbiological factors, bacterial communities, and archaea communities. Biogas production was most effective between days 50 and 90, where gas production was above 0.70 L/d and the CH4 yield was above 0.36 L/g‐volatile solid. The relative abundance of the first dominant bacterial OTU with 99% identity to Clostridium cellulovorans varied between 16.17% and 27.30%. These bacteria typically degrade cellulose and hemicellulose. The second dominant bacterial OTU (relative abundance 15.23%‐27.15%) was 99% identical to Terrisporobacter petrolearius, a typical fermentative species. The most abundant (4.15%‐37.14%) archaeal OTU was 98% identical to Methanocorpusculum sinense, which is a typical hydrogenotrophic methanogen. A low‐temperature biogas metabolic pathway was constructed, based on abundant bacterial and methanogen OTUs. The most suitable metabolic pathway describes that hydrogen is produced by one part of the community and then used to reduce the produced carbon dioxide into CH4; this seems to be the major pathway by which biogas is produced under low‐temperature conditions.

Enhancement of Bioelectrochemical CO2 Reduction with a Carbon Brush Electrode via Direct Electron Transfer

“…Tangfeifania (15.6%) and Aminomonas (9.2%) sequences accounted for the highest proportion of bacterial sequences on the surface of the carbon brush cathode (Figure B). Tangfeifania has been detected in several anaerobic digesters where DIET has been stimulated; , however, its role in these systems has yet to be evaluated. Tangfeifania are fermenters, and their fermentation end products could be providing methanogens in the reactor with such soluble electron sources as hydrogen, formate, and acetate .…”

Determining the Microbial Source of Methane Production in Anaerobic Digestion Systems Through High-Throughput Sequencing Technology

“…Mohammadabadi et al (2021) found the proteolytic bacteria Streptococcus gallolyticus in rumen fluid in great abundance, while the bacterial OTU with the third highest average relative abundance in our study, B-OTU3, showed 100% similarity to Streptococcus gallolyticus and could be considered as almost identical strains. Yang et al (2019) conducted an anaerobic digestion study at 9 °C with pig manure as feedstock and reported that the most abundant bacterial species was the hydrolytic Clostridium cellulovorans, followed by the fermentative bacterium, Terrisporobacter petrolearius.…”

“…Several studies have explored the trophic types of methanogenic group under low-temperature conditions from various perspectives and the results were generally consistent with our outcomes. Yang et al (2019) conducted a study on anaerobic digestion of pig manure at 9 °C and found that the hydrogenotrophic methanogen Methanocorpusculum sinense was the primarily dominant methanogen, with a relative abundance of 4.15-37.14%. Tian et al (2018) studied the dominant methanogenic groups in anaerobic digestion systems at 9, 15, 21, 35, 45, and 55 °C, and concluded that almost all methane was produced through CO 2 reduction by H 2 at low temperatures of 9 °C and 15 °C.…”

Effects of environmental factors on low temperature anaerobic digestion of pig manure

“…Mix equal amounts of samples according to the concentration of PCR products and mix them well, then used 1 × TAE running buffer to make agarose gel (gel concentration is 2%) and conducted electrophoresis, and selected the main band size between 400 and 450 bp [24]. The target bands were recovered by gel tapping, and the PCR products were recovered and purified using The GeneJET Gel Extraction Kit (K069, Thermo Fisher Scientific, USA).…”

“…Many researchers have studied the nutritional types of methanogens under low-temperature conditions from various perspectives, and the results are generally consistent with the results of this study. Yang et al [24] studied the anaerobic digestion of pig manure under 9 °C, and found that the relative abundance of hydrogen trophic methanogens Methanocorpusculum sinense was 4.15%-37.14%, which was the most dominant methanogen. Tian et al [25] studied the dominant methanogenic bacteria in anaerobic digestion system at 9 °C, 15 °C, 21 °C, 35°C, 45 °C and 55 °C respectively, and found that almost all methane came from the hydrogen reducing carbon dioxide pathway at 9 °C and 15 °C.…”