Phenols are very soluble in water; as a result, they can pollute a massive volume of fresh water, wastewater, groundwater, oceans, and soil, negatively affecting plant germination and animal and human health. For the detoxification and bioremediation of phenol in wastewater, phenol biodegradation using novel bacteria isolated from sewage sludge was investigated. Twenty samples from sewage sludge (SS) were collected, and bacteria in SS contents were cultured in the mineral salt agar (MSA) containing phenol (500 mg/L). Twenty colonies (S1 up to S20) were recovered from all the tested SS samples. The characteristics of three bacterial properties, 16S rDNA sequencing, similarities, GenBank accession number, and phylogenetic analysis showed that strains S3, S10, and S18 were Pseudomonas aeruginosa, Klebsiella pneumoniae, and Klebsiella variicola, respectively. P. aeruginosa, K. pneumoniae, and K. variicola were able to degrade 1000 mg/L phenol in the mineral salt medium. The bacterial strains from sewage sludge were efficient in removing 71.70 and 74.67% of phenol at 1000 mg/L within three days and could tolerate high phenol concentrations (2000 mg/L). The findings showed that P. aeruginosa, K. pneumoniae, and K. variicola could potentially treat phenolic water. All soybean and faba bean seeds were germinated after being treated with 250, 500, 750, and 1000 mg/L phenol in a mineral salt medium inoculated with these strains. The highest maximum phenol removal and detoxification rates were P. aeruginosa and K. variicola. These strains may help decompose and detoxify phenol from industrial wastewater with high phenol levels and bioremediating phenol-contaminated soils.
A B S T R A C TThe present study aims to evaluate the removal of phenol and zinc by Candida strains isolated from sludge and wastewater. It also aims to select candidates for biosorption and bioreduction to improve the traditional treatment process of wastewater and produce reclaimed water for irrigation. Forty-one Candida strains (12 Candida tropicalis, 13 Candida lipolytica, 6 Candida maltosa, 10 Candida parasopilis) from sludge and wastewater during treatment of sewage water were screened for their Zn biosorption and phenol removing potential. Four C. tropicalis, 3 C. lipolytica, 2 C. maltose and 6 C. parasopilis strains demonstrated the highest final population (>7 log CFU/ml) after 3 h of exposure to low pH and temperature. The majority of the tested strains were resistant and exhibited partial phenol degrading up to 700 μg/ml. Scanning electron microscopy of Candida indicated that there was neither damage in the cells nor signs of irregular wrinkled outer surface of cells when treated with phenol or Zn compared to the control. These strains are good candidates for further investigation within different sewage treatment plant systems to elucidate their potential biodegradation and bioabsorption of hazard benefits in the system used for treating wastewater.
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