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So far, the information regarding enhanced degradation and biodegradation mechanisms of TPhT, an endocrine disruptor, is severely limited. Whether dearylation during TPhT degradation occurs successively or synchronously is not revealed clearly. To deal with these problems, this study focused on the biodegradation of TPhT and its metabolites by Bacillus thuringiensis through the acceleration of Tween 80. The results showed that Tween 80 obviously increased the TPhT solubility. After degradation by cells in the presence of 80 mg L-1 Tween 80 for 2 d, the residual TPhT at 1 mg L-1 initially was decreased to 48.4%. During the biodegradation process, Tween 80 significantly reduced intracellular Na+, NH+4: and Mg2+ release, and increased extracellular Cl- , PO(3-)4 and K+ utilization. Metabolites analysis revealed that phenyltin biodegradation initially proceeded by cleaving the aromatic ring, not by splitting the covalent bonds between the benzene rings and tin atom. Ring-cleavage reactions in the benzenes of TPhT occurred individually and synchronously, producing diphenyltin, monophenyltin and tin accordingly.

To investigate the pathway and mechanism of triphenyltin (TPhT) biodegradation by Klebsiella pneumoniae, and the effects of TPhT on cells during the degradation process, the alteration of carbon utilization ability of the strain after dealing with different concentrations of TPhT was studied by the Biolog method, and the degradation pathway of TPhT was explored by GC-MS and X-ray photoelectron spectroscopy (XPS). After degradation for 2 h, the nutrient utilization capacity of K. pneumoniae was significantly improved by 1 mg x L(-1) TPhT. Atomic force microscope observation found that exposure to TPhT changed the cellular morphology, inducing the apoptosis of some cells, but most of the cells still maintained intact and had smooth cell wall. The efficiencies of TPhT removal by intracellular enzyme were up to 66.0% within 120 h, which demonstrated that endoenzyme was more effective than the intact cells. The results of GC-MS and XPS revealed that during the biodegradation process, TPhT was transformed to diphenyltin, monophenyltin and finally inorganic tin.

The influence of different metal ions and different forms of addition on triphenyltin enzymatic degradation was investigated under conditions using enzyme obtained from Klebsiella pneumoniae. The objective of this study is to illuminate the mechanism of enzymatic degradation of triphenyltin (TPhT). The results demonstrated that the strain was able to tolerate K+, Mg2+, CU2+, Ca2+ and Fe3+ at high concentrations. High concentrations of Zn2+ and Fe2+ had some toxic effects on the strain, thus affecting its growth. The endoenzyme activity was enhanced by metal ions such as K+, Mg2+, Zn2+, Cu2+ and Fe2+ at certain concentrations. In the presence of 30 mg/L of Mg2+, the removal percentage of TPhT was up to 77.22%. Fe3+ restrained the enzyme activity at certain concentrations. Adding K+, Mg2+, Zn2+, Cu2+ into medium can promote the production of enzyme, among which Mg2+ demonstrated up to 85.66% of removal percentage of TPhT, suggesting some metal ions at the appropriate concentration range can be used as enzyme activator for the enzymatic degradation of triphenyltin. Metal ions showed no relevant impact on the cell growth and enzyme production. Certain metal ions can only serve as activators of endoenzyme and exhibited no similar effect towards exoenzyme.

The biodegradation of triphenyltin (TPT) by Rhodopseudomonos spheroids was investigated in this study. The results illuminated that R. spheroids was an effective strain for the biodegradation of TPT. The maximum removal ratio was attained when the growth temperature of R. spheroids was 30 degrees C. After treating for 3 hours, the removal ratios of 3 mg x L(-1) TPT were 13.82% to 47.29% using 0.49 g x L(-1) (based on dry weight) biomass of R. spheroids. The experiments on biodegradation of TPT were carried out in double-distilled water, simulated seawater,culture medium and river water, respectively. The results demonstrated that river water was optimal for the biodegradation since the indigenous microorganisms in water synergistically increased the removal ratios of TPT. Extracellular enzyme produced by R. spheroids was also effective on the degradation of TPT, and 71.64% of TPT was degraded by this way within 24 hours. The experiments also revealed that the biodegradation process of TPT included biosorption by cell wall, TPT entering cells, and initial degradation by intracellular enzyme, then the TPT and intermediate products backing out of cells to be degraded by extracellular enzyme.

The objective of this study is to illuminate the mechanism of biodegradation of triphenyltin (TPhT). The removal of TPhT by Klebsiella pneumoniae was, therefore, investigated through characteristics studies. The influences of the various parameters were also discussed. The results demonstrated that the cell, extracellular secretion and intracellular enzyme were the effective biomasses for the biodegradation of TPhT. At initial concentration of 3 mg x L(-1), 10.9%, 5.3% and 47.9% of TPhT could be degraded by these biomasses respectively at 30 degrees C within 2 hours under an rotary shaker at 120 r x min(-1). The experimental results also showed that the enzyme activity could be affected by the buffers, pH, temperature, metals and the concentration of TPhT. The degradation efficiency would reach the highest point at pH 8, and at the optimal temperature of 50 degrees C. Metals including Mg2+, Mn2+, Fe2+ and Fe3+ improved the enzyme activity at certain concentrations. In the presence of 15 mg x L(-1) of Mg2+, the removal percentage of TPhT was up to 73.8%. It suggested that the metals activated the enzyme and interacted with the TPhT enabling its removal during the biodegradation process. Linear plots of removal ratios versus concentrations of TPhT meant that the biodegradation fitted the Michaelis-Menten model. The Vmax and Km of this biodegradation were 0. 15 mg x (L x min)(-1) and 47.1 mg x L(-1), respectively.

The biosorption and biodegradation of triphenyltin (TPhT) from aqueous solutions by isolated strains were investigated through microbial separation and characteristic studies. The results illuminated that Klebsiella pneumoniae was an effective strain for the biosorption and removal of TPhT. 70% to 97.9% of TPhT with initial concentration of 3 mg x L(-1) could be absorbed within 2 h, and 26.4% to 54.6% of this TPhT was biodegraded within 5 d using 0.3 g x L(-1) to 3.0 g x L(-1) biomass of K. pneumoniae. TPhT could be more effectively degraded by separated endoenzyme than by cell biomass,and 28.1% to 77.8% of TPhT would be degraded by this way within 2.0 h.The biodegradation experiments also showed that the degradation of TPhT by K. pneumoniae mainly occurred intracellularly and the increase of degradation rate gradually slowed down with time. Separated endoenzyme gave rise to the highest biodegradation of TPhT at the contact time of 2.0 h,while the intact cell achieved the highest rate of biodegradation within 1 d, and then reached a plateau among 2 d to 5 d. The experiments also revealed that the biodegradation process of TPhT included biosorption by cell wall, active transportation across cell membrane, and biodegradation within cytoplasm, in which TPhT bio-adsorbed oh the cell wall increased linearly with time,TPhT inside the cell wall decreased rapidly from 55.9% to 17.0% during the first 3 d, and then turned to smooth; while TPhT in the supernate changed reversely with that occurred inside the cell wall.