Isolation and identification of a heterotrophic nitrifying and aerobic denitrifying Acinetobacter sp．YF14 and its denitrification activity

Abstract:

Abstract:［Objective］We separated，screened and identified a heterotrophic nitrifying and aerobic denitrifying bacterium from the surface sediment of a culture pool． Furthermore，we studied the role it plays in denitrification．［Methods］We separated the bacterium through enrichment culture，identified it by observing its morphological characteristics，studying its physiological and biochemical properties and making phylogenetic analysis of its 16S rDNA sequences． Then we studied the growth curve by regularly measuring the OD600 value，studied the influencing factors and optimum conditions of denitrification through orthogonal experiment，and examined its denitrification activity through interaction with the activated sludge of sewage treatment plant． ［Results］The strain was identified as Acinetobacter and named A．sp．YF14，which is the first known Acinetobacter that carries out heterotrophic nitrification and aerobic denitrification． It reached the logarithmic growth phase after 12 hours，the stationary phase after 22 hours，and the decline phase after 45 hours． Using strain YF14 in a reactor under heterotrophic conditions，the NH +4 -N and total nitrogen removal rates reached 92% and 91% respectively within 3 days． In addition，nitrate and nitrite nitrogen were not observed during the incubation． Under aerobic incubation conditions，almost all of the nitrogen was removed through denitrification in the nitrate or nitrite culture medium inoculated with strain YF14. The orthogonal experiment results indicated that the denitrification effect was optimal when the rotate speed，carbon source，inoculation percentages，carbon nitrogen ratio and pH were 160 r /min，glucose，1% ，8:1 and 6.5，respectively． Sorting Order of the factors on the denitrification effect was rotate speed ＞ inoculation percentages ＞ carbon source ＞ carbon nitrogen ratio ＞ pH． The strain YF14 could improve the denitrification rate by about 30% when interacting with active sludge．［Conclusion］The strain YF14 coupling of heterotrophic nitrification and aerobic denitrification is feasible and is of practical value in water treatment．