Microbial Community Structure And Function In A Lab-scale Denitrifying Quinoline-degrading Bioreactor

Quinoline, which possesses toxic, carcinogenic, and recalcitrant properties,is one of the main nitrogenous heterocyclic compounds in coking wastewater. Itis nessesary to study the quinoline degradation. Previous studies have provedthat quinoline could be degraded under denitifying condition. But little is knownabout the microbial community in the denitrifying quinoline-degrading system.In this study, molecular biological techniques and the pure culture technologywere used to analyze the microbial communities and the metabolism function ofthe predominant bacteria in a lab-scale denitrifying bioreactor for quinolinedegradation.A lab-scale denitrifying bioreactor were acclimated with the cokewastewater treatment seeding sludge and was utilized to degrade quinoline andto remove nitrate. Stable removal efficiencies were achieved after an adaptationperiod of more than half year. The quinoline removel efficiency was about80%and nitrate nitrogen over90%。Firstly, using the pure culture technology, we analyzed26predominantbacterial strains isolated from a denitrifying quinoline-degrading bioreactor. Thecapacity of denitrification and aerobic degradation for quinoline of these strainswas determined. Then the ability of denitrifying degradation of quinoline byselected denitrifying strains was measured. The results showed that10strains ofisolates, which belong to Bacillus, Staphylococcus, Pseudomonas, Brucella andDelftia, were denitrifying bacteria. Whereas,9strains of isolates belonging toRhodococcus had the ability of quinoline degradation under aerobic condition.This part of work described the metabolism function of the major predominantbacteria of microbial community in a quinoline degrading bioreactor. Diverse bacteria, in terms of metabolism, existed in the anoxic denitrifying bioreactor.In order to obtain a deep insight into the bacterial community in thebioreactor, we used denaturing gradient gel electrophoresis technology(DGGE)and454pyrosequencing method. Both DGGE Profile of the16S rRNA gene V3region and the results of comparison of the group distribution at the phylum-,class-, order-, family-, genus-and OTU-level on the basis of bacterial454sequencing data shown that, bacterial community fluctuated first and thenstabilized during the running period. From the results of diversity statistics, thediversity index of the bacteria decreased. After analysing the bacterial OTUswith significant changes, we found that the variation of the bacterial commuitywas mainly the change of relative abundace of aerobic bacteria, denitrifyingbacteria and anaerobic bacteria. Therefore, the change of the bacterialcommunity could be attributed to the change of the oxidation-reductioncondition in the bioreactor. Moreover, Thauera and Denitratisoma, thepredominant groups in the bacterial community under stable state, might be themain functional group of the bioreactor system.In addition, we analysed the archaeal community in the bioreactor with454pyrosequencing method. The results shown that the phylotypes of archaealcommunity was less than bacteria community. During the running period, thediversity index of the archaea decreased and then increased.Methanomethylovorans was the most predominant group in the archaealcommunity. Methanoculleus, Methanofollis, Methanobacterium were also thedominant phylotypes.