Study Of Enrichment And Population Characteristics Of Methanotrophs In An Anaerobic Domestic Landfill Environment

Microbial methane oxidation in landfill is critical for attenuating methane emission to the atmosphere.In the present study,the characteristics of methane biooxidation and methaneoxidizing microorganisms were studied by enrichment cultivation using fresh and aged leachate.This study was helpful for further study of anaerobic oxidation process and microorganisms in landfill and it could also provid guidance for effective methane emission control at landfill sites.The following conclusions are reached.?1?Using NMS as substrate,the daily methane oxidation rate of simulating landfiil leachate under anaerobic incubation could be significantly improved from 0.5%-2% to 2.5%².7%.Based on the existing anaerobic methane oxidation mechanisms,the maximum possible oxidation rate was 39.5%.However,in our study,the anaerobic methane oxidation rates were 36.28%–39.40% in 14 days.?2?The 16 S rRNA gene sequence analysis showed that the genus Methylocystis was the dominant bacteria in aerobic cultures?relative abundance 35.96%–78.37%?.Genus Moheibacter?41.38% in A1?and Cupriavidus?43.08% in A2?were the most dominant taxa in anaerobic cultures.No research has pointed out that Moheibacter and Cupriavidus could conduct methane oxidation neither in aerobic nor in anaerobic condiction.In addition,aerobic methanotrophs Methylocaldum?29.68% in A1?and Methylocystis?6.36% in A2?were also found in anaerobic incubation with low abundance.?3?MOB was incubated successfully under anaerobic environment with leachates which collected from equalization basins of the landfill.The growth curve of MOB showed that the culture cycle for MOB under aerobic and anaerobic condition was 15,and 55 days,respectively.The cumulative CH4 consumption at the end of incubation was 630.9 ± 48.74 ml at anaerobic incubation and 98.37 ± 11.74 ml at aerobic incubation.SO₄^2- and NO3-were extra added to investigate the influence factors of methane oxidation during anaerobic incubation.However,the amount of electron acceptors being added to the incubations were not sufficient to account for the total observed methane oxidation.?4?The 16 S rRNA and pmo A gene sequence analysis showed MOB and related microbes evolved during the incubation.type I MOB affiliated with Methylomonas were the predominant methane oxidizers,accounting for 81% of the total methanotrophic communities during aerobic incubation?sample O1?.However,the relative abundance of type I MOB Methylomonas decreased?48% in A1,8% in A2?while that of type X MOB Methylococcus increased?19% in A1,36% in A2?.Type II MOB Methylocystis?30% in A1,54% in A2?gradually increased with prolonging anaerobic incubation time.Methylococcus finally became dominated methanotrophs?accounting for 65% of the total methanotrophic communities?after 55 days of anaerobic incubation?sample A3?.Archaea Methanosaeta was found in the anaerobic culture which uses acetate as the sole source of energy.Because the amount of electron acceptor was not enough to account for total observed methane oxidation,further studies should be conducted to investigate whether the O2 is intracellularly produced.