Decreasing ruminal methane production through enhancing the sulfate reduction pathway

Methane(CH4)production from ruminants accounts for 16%of the global greenhouse gas emissions and represents 2%to 12%of feed energy.Mitigating CH_(4) production from ruminants is of great importance for sustainable development of the ruminant industry.H_(2) is the primary substrate for CH_(4) production in the processes of ruminal methanogenesis.Sulfate reducing bacteria are able to compete with methanogens for H_(2) in the rumen,and consequently inhibit the methanogenesis.Enhancing the ruminal sulfate reducing pathway is an important approach to mitigate CH_(4) emissions in ruminants.The review summarized the effects of sulfate and elemental S on ruminal methanogenesis,and clarified the related mechanisms through the impacts of sulfate and elemental S on major ruminal sulfate reducing bacteria.Enhancing the activities of the major ruminal sulfate reducing bacteria including Desulfovibrio,Desulfohalobium and Sulfolobus through dietary sulfate addition,elemental S and dried distillers grains with solubles can effectively decrease the ruminal CH_(4) emissions.Suitable levels of dietary addition with different S sources for reducing the ruminal CH_(4) production,as well as maintaining the performance and health of ruminants,need to be investigated in the future.

Near-infrared H_(2)O_(2)production via dual pathways of O_(2)reduction and H_(2)O oxidation

Hydrogen peroxide(H_(2)O_(2))is a chemical that is widely of interest in both environmental and energy fields.On the one hand,as a clean oxidant,H_(2)O_(2)has been commonly used in the field of bleaching,disinfection,and advanced oxidation processes.On the other hand,H_(2)O_(2)has also been explored as a liquid fuel alternative to H_(2)or fossil fuels in fuel cells due to its high energy density.However,the current industrial production of H_(2)O_(2)relies on the anthraquinone(AO)method that involves palladium-catalyzed hydrogenation-oxidation steps.

Determination of carbon-fixing potential of Bathyarchaeota in marine sediment by DNA stable isotope probing analysis

Bathyarchaeota is believed to play a crucial role in the global carbon cycle due to its vast biomass,broad distribution,and diverse habitat.However,its physiological and metabolic features are hard to determine without pure culture.While metagenomic analyses have shown that Bathyarchaeota has a complete inorganic carbon fixation(Wood-Ljungdahl,WL)pathway,no direct functional confirmation has been reported.To explore the inorganic carbon fixation ability of Bathyarchaeota,we used lignin and sodium bicarbonate-^(13)C(NaH^(13)CO_(3))in the long-term incubation of marine sediment samples.We found that Bathyarchaeota grew continuously in the cultivation system with lignin,and its abundance increased up to 15.3 times after10 months,increasing its fraction of all archaea from 30%to 80%.We monitored theδ^(13)C of total organic carbon to identify microbial carbon fixation in the cultivation systems,finding that it increased in the first month while NaH^(13)CO_(3)was present but only increased continuously afterward when lignin was also present.Furthermore,ultracentrifugation was performed on DNA extracted from samples at different cultivation stages to separate DNA of different buoyant densities,and bathyarchaeotal and bacterial 16S ribosomal RNA(r RNA)gene abundance were quantified using qPCR.Compared to bacteria,bathyarchaeotal 16S rRNA tended to be concentrated in heavy layers after 4 months of incubation with lignin and NaH^(13)CO_(3),indicating that Bathyarchaeota DNA contained^(13)C through proliferation based on lignin utilization and NaH^(13)CO_(3)assimilation,proving the carbon fixation capacity of Bathyarchaeota.

Development and characterization of an anaerobic microcosm for reductive dechlorination of PCBs

The toxic and recalcitrant polychlorinated biphenyls （PCBs） adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensively dechlorinate hexa- and hepta-CBs in Aroclor 1260. After 4 months of incubation in defined mineral salts medium amended PCBs （70μmol· L^-1） and lactate （10 mmol· L^-1）, the culture dechlorinated hexa-CBs from 40.2% to 8.7% and hepta-CBs 33.6% to 11.6%, with dechlorination efficiencies of 78.3% and 65.5%, respectively （all in moL ratio）. This dechlorination process led to tetra-CBs （46.4%） as the predominant dechlorination products, followed by penta- （22.1%） and tri-CBs （5.4%）. The number of meta chlorines per biphenyl decreased from 2.50 to 1.41. Results of quantitative real-time PCR show that Dehalococcoides cells increased from 2.39 × 10^5±0.5× 10^5 to 4.99 ×10^7±0.32 ×10^7 copies mL^-1 after 120 days of incubation, suggesting that Dehalococcoides play a major role in reductive dechlorination of PCBs. This study could prove the feasibility of anaerobic reductive culture enrichment for the dehalogenation of highly chlorinated PCBs, which is priorto be applied for in situ biorernediation of notorious halogenated compounds.