Acceleration of tributyltin biodegradation by sediment microorganisms under optimized environmental conditions

The capability of a sediment culture (SED) and bacterial isolate Enterobacter cloacae strain TISTR1971 (B3) to degrade tributyltin (TBT) were optimized by biostimulation; respiration conditions, pH of the media and ambient temperature were studied for more efficient treatment process. Three respiration conditions were investigated; aerobic with/without aeration and anaerobic with 0.1 g NO3− L−1. Among the three conditions, only aeration which provided excess dissolved oxygen, extensively improved the degradation, giving half-lives of 4.08 and 3.16 days for SED and B3, respectively. Variations in the pH of the media (pH 6, 7 and 7.5) moderately affected the degradation rate, mainly at the early stage of log phase. Appropriate pH increased bioavailability by altering Kd and Kow values, and characteristic of TBT. The shortest half-life for SED was 3.53 days at pH 7.5, and 3.10 days for B3 at pH 7. The study of ambient temperature indicated strong uncertainty of degradation from seasonal variation. The half-lives were minimised at 37 °C (3.22 days) for SED and at 28 °C (3.12 days) for B3. Significant variation was shown between 10 and 28 °C, but slightly increased at the higher temperature. This suggests appropriate temperature control at 28 °C for industrial scale treatment. Investigation of these factors together for the optimum conditions lead to modification of the environment, the consequence of which was more efficient biodegradation of TBT in contaminated sediment and water.