Isolation And Identification Analysis Of The Aerobic Denitrifying Bacteria From Sediment In Erhai Lake

ObjectivesWith the rapid development of Chinese economy,the indisciplinable emission ofindustrial waste-water and the domestic sewage,water quality of the lakes is declingand the situation of lake eutrophication is worsening gradually,the phenomena ofwhich made the water blooms occurred frequently.Lake eutrophication has become aincreasingly serious environmental problem which we are facing together,especiallythe nitrogenpollution has impact on people’s living environment, socio-economic andhuman health seriously.Therefore,How to control the nitrogen pollution in water hasbeen the keys to curb the lake eutrophication,because of which the biodenitrificationtechnology has got pro-gaze and popular.Compared with the chemical and physical methods of nitrogen removal,theBiodenitrification technology has its unique advantage.There is no secondarypollution,de-nitrogenizing completely,economic security,and so on.TheBiodenitrification technology is considered as a higher feasible methods of thenitrogen removal technology in the waters.High-activity denitrifying strainscontributes to revealing the denitrification mechanism,optimizing the denitrificationcapability,providing production strains for biological denitrification process.In order toprovide a basis for the later application and management,we picked up one strainEH3-1-4from the Erhai Lake sediment,whose denitrification ability is stronger,and weidentified and study its biodenitrification activity in this study.MethodsIn This project,the culturable denitrifying bacteria was used as the researchobject,which is from the Erhai Lake sediment.The denitrifying bacteria was separatedfrom the Erhai Lake sediment,then We filtered the one whose denitrification rate isfaster.We used three methods to identify the bacteria:Morphological method,physiological and biochemical method,Molecular Biological16S rDNA method.Meanwhile,We measured its growth curve and denitrifying capacity.Results1）In This project,101Strains of denitrifying bacteria were filtered from ten positions of the Erhai Lake sediment.We tested the strains’ denitrifying qualitativesituation in the the colour-reaction whose reaction system is the mixed solution ofP-sulfophenyl sulfonic acid and A-naphthylamine,from which we can pick up the onewhose denitrifying ability is better.Finally,we filtered and obtained one strain whosedenitrifying ability is better,and called it EH3-1-4；2)This bacterial strain is an kind of oxidizing bacteria,it is a rod-shaped andgram negative bacteria.Except the Esterase producing test（Tween80）,Catalasetest,Hydrogen sulfide producing test and amylolysis test are all positive.Sequenceanalysis of16Sr DNA revealed that the series similarity of the strain EH3-1-4and theAchromobacter xylosoxidans is higher,about90pecent.Compared with the threemethods,we tested the homology of gene sequence and phylogenetic analyses. It canbe believed that the strain EH3-1-4belongs to Alcaligenes；3)The research focused on the growth curve found that the logarithmic phase ofthe strain EH3-1-4started after12hours as it began to grow.Then Stable growthperiod started after36hours,and this phase was longer. Its generation cycle was33hours.By testing and analyzing the denitrifying ability of the bacteria,the strainEH3-1-4can biodegrade nitrates effectively in the waters.The highest bacteriaconcentration appeared after36hours as we cultured them and its rate of degradationcould reached71percent.The highest rate of degradation of nitrate nitrogen couldreached1.79mg/L h.Conclusions1)In This study,we picked up and filtered one strain of denitrifying bacteria,whose denitrification ability is stronger,and named EH3-1-4；2)Compared with the three methods,which are Morphological method,Physiological and Biochemical method, Molecular Biological16S rDNA method,thenwe tested the homology of gene sequence and phylogenetic analyses.It can be believedthat the strain EH3-1-4belongs to Alcaligenes（Achromobacter）；.3)By testing and analyzing the denitrifying ability of the bacteria,the strainEH3-1-4can biodegrade nitrates effectively in the waters.It is believed that this strainhas better denitrifying ability. It is proved that the target strain possesses a vast rangeof application prospect.The results of this study have a vital value for furtherapplications.