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Abstract
Recombinant Escherichia coli cells expressing phenol hydroxylase (designated as strain PH^sub IND^) were used to synthesize chloro-substituted indigoids by the transformation of indoles. The optimal conditions for the biotransformation of 4- and 7-chloroindole were determined by response surface methodology. Biotransformation kinetic assays revealed that strain PH^sub IND^ showed high catalytic efficiency for 4- and 7-chloroindole. The formation rate of 7,7'-dichloroindigo (1.35 unit/mg cell dry weight) by strain PH^sub IND^ was 1.14-fold higher than that of 4,4'-dichloroindigo. The intermediates of 7-chloroindole biotransformation were identified by high-performance liquid chromatography-mass spectroscopy, and the biotransformation mechanism was also proposed. These results suggested that there was a potential application of strain PH^sub IND^ in the biotransformation of chloro-substituted indoles to valuable indigoids.[PUBLICATION ABSTRACT]