Chemoenzymatic production of isatin as a bio-red dye from tryptophan using indigo-producing E. coli whole-cell system and hydrogen peroxide-mediated oxidation

초록

Isatin (1H-indole-2,3-dione) is an indole-derived compound with diverse pharmacological properties and industrial applications. However, selective production strategies for isatin from indigo remain limited with chemical synthesis and plant-derived sources. In this study, bioindigo was produced from tryptophan using recombinant Escherichia coli expressing tryptophanase (tnaA) and flavin-containing monooxygenase (FMO), and subsequently converted to isatin through controlled H2O2-mediated oxidation. Under optimized conditions (1 eq H2O2, pH 6.5, 70 degrees C, 96 h), the conversion to isatin reached 65% from bioindigo, comparable to that obtained from commercial indigo under similar oxidation conditions. The recovered isatin was further applied to poly(3-hydroxybutyrate) (PHB) film coloration as a proof-of-concept application, where the isatin-PHB films exhibited biodegradation behavior comparable to that of the other chemical-PHB films. This study demonstrates the feasibility of integrating microbial indigo biosynthesis from tryptophan with subsequent chemical oxidation for isatin production.

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