Isolation And Identification Of Heterotrophic Nitrification Bacteria And Action Effect

Two heterotrophic nitrification strains,named LQ1 and WY1,were isolated from water and sediment in late shrimp farming,respectively.In the light of their morphological and physiological features as well as the 16S rDNA sequences,LQ1 and WY1 were identified as Oceanimonas denitrificans and Acinetobacter lwoffi.Effect of physical and chemical factors on the nitrite nitrogen removal by strain LQ1,was studied,and the optimal conditions of removing efficiently the nitrite nitrogen in water of late shrimp farming was determined;Effect of the initial concentration of nitrogen on strains WY1 growth was analyzed,while the Nitrite nitrogen removal mechanism of two strains was studied preliminary.The results showed that:the optimal conditions of removing efficiently the nitrite nitrogen by LQ-1 were:C/N ratio 19,pH9,temperature 35?,salinity 20,and the optimal conditions of removing efficiently the nitrite nitrogen in water of late shrimp farming by LQ-1 were:sucrose 0.05g/100ml,the concentration of bacteria 0.25ml/100ml,the temperature 30?,and the limiting factor of removing the nitrite nitrogen in water of late shrimp farming was carbon;the optimum initial NaNO₂ concentration of WY-1 was 0.4g/L,and the high initial concentration could inhibit the growth of the strain.Sodium nitrite did not detected at the initial NaNO₂ concentration of 56.7mg/L for strains LQ-1 and WY-1.Denitrification pathway of LQ-1 was preliminary determinated that NO₂-N is first converted into NO₃-N,and NO₃-N was used to synthesize bacterial protein,after some time,NO₂-N is converted into NH₄-N by reduction reaction,no denitrification in the whole process.Denitrification pathway of WY-1 was preliminary determinated that srain WY-1 is converted into NO₃-N and NH₄-N in the metabolic process,and eventually all of them were synthesized into bacterial protein.In this study,two efficient heterotrophic denitrifying bacteria separating and screening have important applications value to solve the excessively high concentrations of nitrite in water of late shrimp farming.