Reduction of the Substrate Toxicity by Persolvent Fermentation: Biodegradation of Indole at High Concentration by Persolvent Fermentation with Pseudomonas sp. ST-200
Noriyuki DOUKYU and Rikizo AONO
Department of Bioengineering, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226, Japan
Pseudomonas sp. strain ST-200 grew on indole as a sole carbon source. lndole is generally toxic to microorganisms. The minimal inhibitory concentration of indole was 0.3 mg/ml for ST-200. However, ST-200 grew in a persolvent fermentation system (a two-phase system consisting of medium and hydrophobic organic solvent) containing a large amount of indole (a medium containing 20% by vol. diphenylmethane and 4 mg/ml indole), because the indole was partitioned preferably in the organic solvent layer. The persolvent fermentation method is likely useful to reduce toxicities of various hydrophobic substrates by lowering the concentration in the medium. When the organism was grown in the medium containing indole at 1 mg/ml in the presence of diphenylmethane, more than 98 % of the indole was consumed after 48 h. Isatic acid (0.4 mg/ml) and isatin (0.03 mg/ml) were produced as the metabolites in the aqueous medium layer. Small amounts of blue indigo and purple indirubin were produced in the organic solvent layer.
