Isolation and Identification of a Denitrifying Pichia sp.Y-4 and Its Ammonia Nitrogen Degradation Performance
At present,ammonia nitrogen pollution in water resources is severe,and environmental governance is urgent.Screening efficient and safe denitrification strains can provide more choices for wastewater denitri-fication.Strains capable of degrading ammonia nitrogen were isolated and screened from biogas fermentation sludge in this study.The selected excellent strains were identified by 18S rDNA sequence analysis.At the same time,single factor and orthogonal experiments were used to explore the optimal nitrogen removal condi-tions[culture temperature,initial pH value,salt concentration,carbon-nitrogen ratio(C/N)]and the nitrifi-cation and denitrification capacity of the strain.The results showed that a wild-type strain of Pichia sp.Y-4 with strong denitrification ability was isolated and screened.After experimental optimization,the optimal denitrification conditions for strain Y-4 are temperature 25 ℃,initial pH value 8.0,salt concentration(NaCl concentration)30 g/L,and carbon-nitrogen ratio 30.After 24 h of culture,the degradation rate of nitrite ni-trogen(NO2--N)by strain Y-4 was 80.50％,and the degradation rate of ammonia nitrogen(NH4+-N)by strain Y-4 was 99.92％after 48 h of culture.The heterotrophic nitrification and aerobic denitrification rates of strain Y-4 within 24 h reached 6.25 mg/(L·h)and 6.71 mg/(L·h),respectively,indicating that Pichia sp.Y-4 has certain application value and potential for wastewater nitrogen pollution treatment and bioremedi-ation.
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