Biodegradation of Pharmaceutical Wastes in Treated Sewage Effluents by Bacillus subtilis 1556WTNC

Abstract

The aim of this study was to investigate the potentials for enzymatic biodegradation of pharmaceutical active compounds (β-lactam antibiotics) in treated sewage effluents as a function of β-lactamase produced Bacillus subtilis 1556WTNC. Four β-lactams antibiotics were selected: two of them belong to penicillin's (amoxicillin and ampicillin) and two belong to cephalosporins (cephalexin and cefuroxime); ciprofloxacin (belongs to quinolones) was used as a negative control. The enzymatic biodegradation process was conducted under the optimal conditions for β-lactams production (5.9 log10 CFU mL-1; pH 6.5; temperature 35 °C for 12 days) as determined in this research. The maximum biodegradation was 25.03 % at 1 mg mL-1 for amoxicillin, 15.59 % at 0.8 mg mL-1 of ampicillin, 22.59 % at 1 mg mL-1 of cephalexin, 10.62 % at 1 mg mL-1 of cefuroxime, while it was 2.45 % at 0.6 mg mL-1 of ciprofloxacin. B. subtilis 1556WTNC exhibited the potential to produce β-lactamase and biodegrade β-lactam antibiotic genetically and inducibly B. subtilis 1556WTNC could grow and biodegrade β-lactam antibiotics in conditions similar to the characteristics of treated sewage effluents such as pH, temperature, and during short time (12 days), because it was already acclimatized to those conditions. For this reason, treated sewage effluents were used as source to isolate this strain. It can be concluded that B. subtilis 1556WTNC is suitable to remove pharmaceutical residues from the treated sewage effluents and produce effluents at higher quality than that achieved by secondary treatment process.