Study On Metabolites Involved In The Methanogenic Biodegradation Of Hydrocarbons

In this study, through methanogenic consortia degrading hexadecane under mesophilic conditions(35oC) as inoculum, using isotopically labeled alkanes, method of GC-MS analysis were applied todetect the characteristic putative metabolites in methanogenic hexadecane degradation, the fndingssupport the proposed novel metabolic mechanism. The analysis of the structures and dynamics of themicrobial communities during the successive transfers of a thermophilic(55oC) methanogenichexadecane-degrading consortium,the results substantially expand the knowledge of the extent ofbacterial diversity associated with the anaerobic degradation of alkanes under thermophilic conditions.In comparison with curde oil hydrocarbons, coal is another kind of fossil fuel. Through addition ofnutrients or a microbial consortium, we used laboratory-scale simulation study in anaerobicbiodegradation of coal samples with different maturity, and high-throughput sequencing method revealsmicrobial species diversity of the coals in situ, collectively, gaining a further understanding of anaerobichydrocarbons degradation processes.In conclusion:(1)Through GC-MS analysis of the metabolites in methanogenic hexadecaneanaerobic degradation, we found three key putative metabolites in extracts of consortium, wehypothesized that activating hexadecane is via exogenous CO2addition in methanogenic conditions,which is different from the carboxylation or fumrate addition reaction under nitrate-reducing orsulfate-reducing conditions demonstrated in the previous literatures. This indicates alternativemechanisms of hexadecane activation may operate under the methanogenic conditions.(2)Sampling125,159and223days enrichment cultures, and analysing the microbial communities diversity viaT-RFLP methods, the results reveal that the family Syntrophaceae is probably the key microbialphylotypes in it. Addition of the putative metabolites as sole carbon resource, the abundance ofSyntrophaceae is significantly improved, which is a practical way to isolate the key anaerobicmirobes.(3) The structures and dynamics of the methanogenic hexadecane-degrading consortium at55°C during successive transfers were examined by T-RFLP and sequencing of16S rRNA genefragments,the results reveal that the concurrence of hydrogenotrophic Methanothermobacter andacetoclastic Methanosaeta species,over four fifths of the bacterial clones in the hexadecane-degradingsubcultures exhibited less than90%similarity to sequences of known type strains, and clones weremainly grouped into unclassified bacteria,which were likely candidates to be involved in hexadecanedegradation under thermophilic conditions.(4)With addition of nutritions and enrichment cultures, themicrobial rate-limiting steps of coal biodegradation can be enhanced. Without addition of nutritions andinoculum, biogenic methane produced in some individual high rank coals, understanding microbial gassystems and estimating production of the biogenic methane-generating within coals of different maturityis the key way to estimate the CBM reserves and exploitation.