Debutylation and Dephenylation of Organotin Compounds Through Fungal Laccase-Mediator Systems

In this study, the biodegradation of tetrabutyltin (TeBT) and tetraphenyltin (TePhT) through various laccase-mediator systems were investigated. The fungal laccases used were from the extracellular fluid of solid fermentation culture of white-rot fungi Perenniporia tephropora TFRI 707, Agrocybe aegerita, and Pleurotus geesteranus, with 2,2-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid), violuric acid, 4-hydroxyacetophenone, and syringaldehyde being used as mediators. After 7 days of incubation, 300 g/L of TeBT or 1000 g/L of TePhT were added, the laccase obtained from P. tephropora TFRI 707 removed 83.9%-87.4% of TeBT and 78.0%-91.9% of TePhT; the laccase obtained from A. aegerita removed 73.7%-88.9% of TeBT and 75.5%-92.0% of TePhT; and the laccase obtained from Pl. geesteranus removed 70.4%-85.3% of TeBT and 72.9%-90.2% of TePhT (percentages include incubation with and without mediators). Tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) were detected during the degradation of TeBT. Triphenyltin (TPhT), diphenyltin (DPhT), and monophenyltin (MPhT) were detected during the degradation of TePhT. Therefore, laccases can effectively and rapidly remove butyl or phenyl side chains from the organotin compounds. Because dealkylated alkyl organotin compounds and the elemental tin exhibit considerably low toxicity, laccases can potentially be used in environmental cleanup.