Screening and Molecular Identification of p-Nitrophenol Degrading Microorganisms

p-Nitrophenol (PNP) is a toxic nitro-aromatic compound widely used in the manufacture of pesticides, dyes, pharmaceuticals and explosives. Due to its extensive industrial applications, PNP frequently contaminates soil and aquatic environments, posing serious ecological and health hazards. The present study aimed to isolate, screen and characterize efficient PNP-degrading microorganisms from environmental samples. A total of seventy-eight soil and water samples were collected from agricultural lands, industrial areas and the hypersaline Lonar Lake in Aurangabad, India. Enrichment culture technique using mineral salt glucose medium supplemented with 100 ppm PNP was employed to selectively isolate PNP-utilizing microorganisms. After successive enrichment and acclimatization, microorganisms were isolated and screened for their ability to degrade PNP. Primary screening was performed based on growth and colour change of the medium, while secondary screening involved spectrophotometric estimation of PNP degradation and nitrite production. Among the isolates obtained, fifteen bacterial strains, four actinomycetal strains and four fungal strains showed the ability to degrade PNP. Based on degradation efficiency, Bacterial strain B15, Actinomycetal strain A5, and Fungal strain R8 were identified as the most potent degraders. These isolates were further characterized through morphological, physiological and biochemical tests. Molecular identification using 16S rRNA gene sequencing confirmed the identity of the efficient bacterial and actinomycetal isolates. The selected strains were further evaluated for various growth parameters including pH, temperature, substrate concentration and the influence of different carbon and nitrogen sources. The results demonstrated that indigenous microorganisms from contaminated environments possess significant potential for the biodegradation of p-nitrophenol. These microbial strains could be utilized in the development of effective bioremediation strategies for detoxification of PNP-contaminated environments.