Degradation of some benzodiazepines by a laccase-mediated system in aqueous solution.

Purified laccase from the soil ascomycete, Paraconiothyrium variabile was employed in the degradation of 7 benzodiazepine substances in the absence and presence of the enzyme mediators, 1-hydroxybenzotriazole (HBT), 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS), 2,6-dimethoxyphenol (DMP), and vanillic acid (VA). In the absence of a laccase mediator, the original concentrations of 10 µg mL(-1) of nitrazepam, alprazolam, diazepam, and oxazepam decreased by 27.3%, 45.6%, 18.6% and 18.7%, respectively, after 48 h treatment using the purified enzyme, whereas the removal percentages for clobazam, chlordiazepoxide, and lorazepam were only 5.6%, 3.6%, and 4.1%, respectively. Among the laccase mediators, HBT was the most efficient compound, increasing the degradation percentages of nitrazepam, alprazolam, diazepam, and oxazepam to 73%, 88.1%, 61.4%, and 71.2%, respectively. The removal percentages of clobazam, chlordiazepoxide, and lorazepam was increased to 8.2%, 4.7%, and 6.5%, respectively, when the laccase-HBT system was used. The data presented suggest that the laccase-mediated system has potential for the elimination of some benzodiazepines in aqueous solution.

Removal of chlorophenolic derivatives by soil isolated ascomycete of Paraconiothyrium variabile and studying the role of its extracellular laccase.

The ability of Paraconiothyrium variabile, a laccase producing ascomycete recently isolated from soil, was studied to eliminate chlorophenol derivatives in submerged culture medium. Among the tested compounds, ρ-chlorophenol (ρ-CP) and pentachlorophenol (PCP) were found to have minimum and maximum toxic effects, respectively, on the growth of the microorganism and at the same time high and low bioelimination percentages. The fungal strain was able to remove 86% of ρ-CP (with initial concentration of 40 mg l(-1)) and 56% of 2,4-dichlorophenol (2,4-DCP; with same concentration as ρ-CP) after 9 days of incubation while no elimination was observed in the presence of 2,4,6-trichlorophenol (2,4,6-TCP) and PCP. Monitoring of laccase production level in the fermentation broth together with pollutant removal confirmed the key role of this copper-containing oxidase in chlorophenol derivatives elimination. The type of laccase inducer (guaiacol) and its final concentration (250 µM) and also initial pH of the fermentation broth (pH=5.5) in the elimination of ρ-CP increased the final removal yield from 86% to 94.3%.