[Enhancing effect of Tween 80 on degradation of triphenyltin by Bacillus thuringiensis].

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.

[Characteristic and ion exchanges during Cu2+ and Cd2+ biosorption by Stenotrophomonas maltophilia].

The characteristics of Cu2+ and Cd2+ biosorption by Stenotrophomonas maltophilia (S. maltophilia) under different biomass, metal concentration and glutaraldehyde content were studied and the correlations among metal biosorption, NO3- removal and ion release were analyzed. The mechanism was explored through ion biosorption, exchange, conversion and release. The experimental results demonstrated that S. maltophilia was an efficient strain to remove Cu2+ and Cd2+. The biosorption efficiencies of Cu2+ and Cd2+ achieved 96.3% and 83.9%, respectively after dealing with 0.05 mmol x L(-1) aqueous solutions for 120 min with dry biosorbent dosage of 0.2 g x L(-1). Cu2+ and Cd2+ biosorption by S. maltophilia included surface adsorption, transmembrane active transportation, bioaccumulation of NO3- and reduction of NO3- to NO2-. The intracellular transfer and reduction of NO3- to NO2- during biosorption by S. maltophilia were energy-consuming biological processes. It could also promote the release of Cl-, PO4(3-), SO-4(2-), Na+, NH4+, K+ and Ca2+. From FTIR investigation, involvement of various functional groups like acetylamino, hydroxyl and carboxyl in the binding of Cu2+ and Cd2+ was evident. Moreover, XPS results proved that the valence state of Cu2+ and Cd2+ did not changed by biosorption.