Biodegradation of endocrine disrupting compounds from the wastewater by the immobilized indigenous bacteria

Abstract

4-tert-octyl phenol is one of the important endrocrine-disrupting compounds and is considered a major health hazard. A total of six isolates degraded 4-tert-octylphenol, and the strains Bacillus velezensis LG16 and Pseudomonas aeruginosa AC20 exhibited maximum 4-tert-octylphenol degradation. Co-culture of these two strains improved 4-tert-octylphenol degradation from the wastewater. One variable at a time approach showed that 40°C incubation temperature, pH 8.0, and an initial 4-tert-octylphenol (60 mg/L) influenced biodegradation. The bacterial strains were immobilized in sodium alginate beads, and improved biodegradation was achieved. The biocatalytic process mediated by the immobilized cells was optimized by a statistical approach (two-level full factorial design and response surface methodology). In a two-level factorial model, 4-tert-octylphenol degradation varied from 1.1% to 55.2%. The 4-tert-octylphenol degradation was maximum at pH 6, 0.01 mg/L 4-tert-octylphenol, and 10 mg/L glucose with 20 g beads/L. ANOVA revealed that the designed model was statistically significant (p = 0.0310). A central composite design was used to analyze the interactive effect of significant variables and to explore the optimum conditions for 4-tert-octylphenol degradation by immobilized bacteria. The maximum phenol degradation was observed (97.4%) at pH 7.0, 0.06 4-tert-octylphenol, and 13.75 g sodium alginate beads/L. ANOVA showed that the designed model was statistically significant (p = 0.0091). The designed CCD model, the correlation coefficient value, and the lack of fit value showed that the designed CCD model was significant. The immobilized bacterial cells could more effectively degrade 4-tert-octylphenol than free bacterial cells. The high degradation potential indicated its application in degrading 4-tert-octylphenol from wastewater under optimized conditions.