Aerobic methane oxidizing bacteria (methanotrophs) can use methane as carbon source and energy source, eliminating 10%-20% of global methane. Methanotrophs can also effectively synthesize valuable methane-derived products. This article introduced the methane oxidizing mechanism of methanotrophs, and summarized the practical application and research hotspots of methanotrophs in the field of methane emission reduction in the landfill, ventilation air methane mitigation in coal mines, valuable chemicals biosynthesis, as well as oil and gas reservoir exploration. Main factors influencing the pollutant removal and the biosynthesis efficiency in various applications were also discussed. Based on the study of large-scale cultivation of methanotrophs, some measures to benefit the application and promotion of aerobic methane oxidizing biotechnology were proposed. This includes investigating the effect of intermediate metabolites on methanotrophs activity and population structure, and exploiting economical and efficient alternative culture media and culture techniques.
Biotechnology ; Carbon ; Culture Media/chemistry* ; Methane/metabolism* ; Methylococcaceae/metabolism* ; Oxidation-Reduction

The effect of tea saponins (TS) on rumen fermentation and methane emission was examined using an in vitro gas production technique named Reading Pressure Technique. Three levels of TS addition (0, 0.2, 0.4 mg/ml) were evaluated in the faunated and defaunated rumen fluid. Compared to the control, TS addition decreased the 24 h gas production in the faunated rumen fluid, but had a minor effect on gas yield in the defaunated rumen fluid. The TS significantly reduced methane production in vitro. In the faunated rumen fluid, 0.2 or 0.4 mg/ml TS decreased the 24 h methane emission by 12.7% or 14.0%, respectively. Rumen fluid pH value was affected neither by TS addition nor by defaunation. The TS addition had only minor effects on volatile fatty acids, but the yield and pattern of volatile fatty acids were greatly affected by defaunation. While the molar proportion of acetate was not affected by defaunation, the propionate was significantly increased and the butyrate significantly decreased. Ammonia-N concentration and microbial protein yield were influenced by TS inclusion and defaunation. Inclusion of 0.4 mg/ml TS increased the microbial protein mass by 18.4% and 13.8% and decreased the ammonia-N concentration by 8.3% and 19.6% in the faunated and defaunated rumen fluid, respectively. Protozoa counts were significantly reduced by TS inclusion. The current study demonstrated the beneficial effect of TS on methane production and rumen fermentation, and indicated that this may be due to the effect of the associated depression on protozoa counts.
Animals ; Camellia sinensis ; metabolism ; Eukaryota ; drug effects ; physiology ; Fermentation ; drug effects ; Gastrointestinal Contents ; drug effects ; microbiology ; In Vitro Techniques ; Methane ; metabolism ; Plant Extracts ; pharmacology ; Rumen ; metabolism ; microbiology ; Saponins ; pharmacology ; Seeds ; metabolism ; Sheep ; Tea ; chemistry

Colocolic fistulas are usually a complication of an inflammatory or neoplastic process. Development of these abnormal bowel communications may lead to bacterial overgrowth. We report on a 71-year-old man with a one-year history of recurrent abdominal distension and irregular bowel habits. Abdominal X-rays and computed tomography showed multiple air-fluid levels and loops of distended bowel without evidence of mechanical obstruction or diverticulitis. Colonoscopy showed a fistulous tract between the sigmoid colon and cecum. Results of a lactulose breath test showed high fasting breath CH4 levels, which were thought to be the result of intestinal bacterial overgrowth. The patient was diagnosed with a colonic pseudo-obstruction associated with bacterial overgrowth due to a sigmoidocecal fistula. We recommended surgical correction of the sigmoidocecal fistula; however, the patient requested medical treatment. After antibiotic therapy, the patient still had mild symptoms but no acute exacerbations.
Aged ; Anti-Bacterial Agents/therapeutic use ; Breath Tests ; Colonic Pseudo-Obstruction/*diagnosis/etiology ; Colonoscopy ; Humans ; Intestinal Fistula/*diagnosis/drug therapy/microbiology ; Male ; Methane/chemistry/metabolism ; Tomography, X-Ray Computed