Biodegradation of 17 β-estradiol by Serratia marcescens and Stenotrophomonas tumulicola co-culture isolated from a sewage treatment plant in Upper Egypt

Background and Objectives: 17 β- estradiol (E2) is an important pollutant of the aquatic system. It is responsible for sexual disruptions in the majority of aquatic organisms. This study aimed to search for bacteria with high potential degradation of E2 as an important method for bioremediation. Materials and Methods: Sewage water samples were collected and treated to isolate bacterial strains which were identified by conventional methods and 16S ribosomal RNA gene sequence analysis. The biodegradation of E2 by the isolated strains was evaluated under different environmental conditions. Results: Two bacterial strains were recovered from sewage water samples and identified as Stenotrophomonas tumulicola and Serratia marcescens, (named ASc2 and ASc5 respectively). Co-culture of the two strains showed biodegradation of approximately 93.6 % of E2 (50 mg. L^-1) within 48 hours. However, the biodegradation capacity of the same E2 concentra- tion was 69.4% and 71.2% for ASc2 and ASc5 each alone, respectively. The optimum cultivation conditions for efficient E2 biodegradation by co-culture were 5% (v/v) inoculation volume with 50 mg. L^-1 of E2 as the initial concentration at pH 7 and 30°C within 48 hours inoculation period. Conclusion: This study detected new bacterial strains that are capable of rapid degradation of estrogen as an environmental pollutant.