Laccase-mediated synthesis of a phenoxazine compound with antioxidative and dyeing properties--the optimisation process.

This study demonstrates the optimisation of the main parameters of the laccase-mediated biosynthesis of high-intensity-coloured orange phenoxazine compound, 2-amino-3-oxo-3H-phenoxazine-8-sulfonic acid, and the antioxidative and dyeing properties. Among optimised parameters were the pH value, the activity of laccase, and the high concentration of the precursor as the necessary step in terms of dye synthesis scale-up. The high concentration of the precursor of ca. 10 g/L can be transformed totally by laccase at the activity of 30 U/g during 12 hours, in an optimised and standardised process in nearly 100% yield of synthesis. The obtained dye exhibited good dyeing properties determined according to the ISO standards. Antioxidative activities were detected for phenoxazinone dye using two independent methods, the chemiluminescence assay and the ABTS free radical-scavenging test, with the values of EC50 for the tested phenoxazine dye amounting 189.8 μg/mL and 1428 μg/mL, respectively. Despite the presence of the phenoxazine core in the structure of this dye, no antibacterial capacity was noted.