Nitrous oxide respiring bacteria in biogas digestates for reduced agricultural emissions

Inoculating agricultural soils with nitrous oxide respiring bacteria (NRB) can reduce N2O-emission, but would be impractical as a standalone operation. Here we demonstrate that digestates obtained after biogas production are suitable substrates and vectors for NRB. We show that indigenous NRB in digestates grew to high abundance during anaerobic enrichment under N2O. Gas-kinetics and meta-omic analyses showed that these NRB’s, recovered as metagenome-assembled genomes (MAGs), grew by harvesting fermentation intermediates of the methanogenic consortium. Three NRB’s were isolated, one of which matched the recovered MAG of a Dechloromonas, deemed by proteomics to be the dominant producer of N2O-reductase in the enrichment. While the isolates harbored genes required for a full denitrification pathway and could thus both produce and sequester N2O, their regulatory traits predicted that they act as N2O sinks in soil, which was confirmed experimentally. The isolates were grown by aerobic respiration in digestates, and fertilization with these NRB-enriched digestates reduced N2O emissions from soil. Our use of digestates for low-cost and large-scale inoculation with NRB in soil can be taken as a blueprint for future applications of this powerful instrument to engineer the soil microbiome, be it for enhancing plant growth, bioremediation, or any other desirable function.

Bacteria in biogas digestates for reduced climate forcing

Mitigation of N2O-emissions from soils is needed to reduce climate forcing by food production. Inoculating soils with N2O-reducing bacteria would be effective, but costly and impractical as a standalone operation. Here we demonstrate that digestates obtained after biogas production may provide a low-cost and widely applicable solution. Firstly, we show that indigenous N2O-reducing bacteria in digestates grow to high levels during anaerobic enrichment under N2O. Gas kinetics and meta-omic analysis show that the N2O-respiring organisms, recovered as metagenome-assembled genomes (MAGs), grow by harvesting fermentation intermediates of the methanogenic consortium. Three digestate-derived denitrifying, N2O-reducing bacteria were obtained through isolation, one of which matched the recovered MAG of a dominant Dechloromonas-affiliated N2O reducer. While the identified N2O-reducers encoded genes required for a full denitrification pathway and could thus both produce and sequester N2O, their regulatory traits predicted that they act as N2O-sinks. Secondly, moving towards practical application, we show that these isolates grow by aerobic respiration in digestates, and that fertilization with these enriched digestates reduces N2O emissions. This shows that the ongoing implementation of biogas production in agriculture opens a new avenue for cheap and effective reduction of N2O emissions from food production.

Influence Of Organic Matrix And Cations On Bio-Methane Yield With Anthracite Methanogenic Consortium

Organic compounds fermentation of coal has been used to generate secondary biogenic gas and enhance gas reservoirs in coal bed. To enhance the bio-degradation process, culture nutrition plays an important role in remediating the nutritional deficiency of the coal seam. The influence of bio-methane yield with organic inputs and cation concentrations was examined. Research of organic matrix influence revealed that the traditional organic material except yeast extract should forbid, and the input of yeast extract should limit at 1.00g/L also. Further, the study demonstrated that the ion concentration of sodium, potassium, magnesium, calcium and ammonia nitrogen also influenced methane and carbon dioxide yields. And the optimize concentrations for Ca2+, K+, Na+, Mg2+ were 5.1, 1.7, 23 and 1.3 mmol/L. The Mg2+ was particularly sensitive in inhibiting CH4 metabolism processes largely for gas-coal methanogenic consortium.

Influence of Organic Matrix and Cations on Bio-Methane Yield with Anthracite Methanogenic Consortium

Organic compounds fermentation of coal has been used to generate secondary biogenic gas and enhance gas reservoirs in coalbed. To enhance the bio-degradation process, culture nutrition plays an important role in remediating the nutritional deficiency of the coal seam. The influence of bio-methane yield with organic inputs and cations concentrations was examined. Research of organic matrix influence revealed that the traditional organic material except yeast extract should forbid, and the input of yeast extract should limit at 1.00g/L also. Further, the study demonstrated that the ion concentration of sodium, potassium, magnesium, calcium and ammonia nitrogen also influenced methane and carbon dioxide yields. And the optimize concentrations for Ca2+, K+, Na+, Mg2+ were 5.1, 1.7, 23 and 1.3 mmol/L. The Mg2+ was particularly sensitive in inhibiting CH4 metabolism processes largely for gas-coal methanogenic consortium.