Bio-indigo production in two different fermentation systems using recombinant Escherichia coli cells harboring a flavin-containing monooxygenase gene (fmo)

Abstract

Bio-indigo was produced in 3000-L batch and 5-L continuous fermentation of a recombinant Escherichia coli DH5α harboring a novel gene encoding flavin-containing monooxygenase (FMO). Batch fermentation in a 3000-L fermenter produced 911±22mgL−1 of indigo from 2gL−1 tryptophan as a substrate (yield 46.9%) under the following culture conditions as follows: culture temperature 30°C, pH 7.0, agitation speed 200rpm, and aeration 3vvm. Sufficient oxygen (aeration rate and agitation speed) was critical for bio-indigo production. For continuous fermentation in a 5-L fermenter, the volumetric productivity was found to be 11.3mgL−1h−1 up to 110h (final accumulated bio-indigo was 23g) with a constant dilution rate (D) of 0.084h−1 (constant feeding rate of 0.167Lh−1 with medium containing 3gL−1 tryptophan). Recombinant E. coli cells have the ability to withstand the toxicity of high concentration of accumulated indigo in batch fermentation. In continuous fermentation, the recombinant cells exhibited high plasmid stability up to 110h, after which they lost the plasmid.