Enzymatic synthesis of indigo-derivative industrial dyes

Synthetic indigo is among the most important industrial dyes. Unfortunately, synthetic indigo has raised environmental concern due to the use of pollutant and hazardous chemicals. In response, green chemistry aims to find new environmentally friendly and economically attractive synthesis methods. Accordingly, this work describes the enzymatic synthesis of indigo and its derivatives starting from indole. A variant of the heme domain of cytochrome P450 from Bacillus megaterium, CYP(BM3)F87A, was used to catalyze the synthesis of indigo and three di-substituted derivatives. Substrates transformed by a peroxygenase reaction were indole, 4-bromoindole, 5-methoxyindole and 7-methoxyindole. The kinetic data fitted to Hill's mathematical model with k(cat) values of 3.51, 0.94, 4.72, and 4.28 min(-1) for each substrate, respectively. In all cases, colored products were obtained that were characterized by spectrometric techniques. Furthermore, the CYP(BM3)F87A enzyme was immobilized on magnetic nanoparticles that exhibited catalytic rate in the synthesis of indigo from indole (k(cat )0.72 min(-1)). Our results show that enzymatic synthesis of industrial dyes without the use of expensive cofactors offers an attractive and plausible alternative to conventional chemical synthesis with a lower environment impact.