Dye dispersion and the interaction efficiency between azoreductases and dye molecules are rate-limiting steps for the decolorization of azo dyes. In this study, a biosurfactant-producing strain, Pseudomonas taiwanensis L1011, was isolated from crude oil. To increase the yield of the biosurfactant BS-L1011 from P. taiwanensis L1011, culture conditions were optimized including temperature, initial pH, carbon source, nitrogen source and C/N ratio. A maximum yield of 1.12g/L of BS-L1011 was obtained using D-mannitol as carbon source and yeast extract/urea as compound nitrogen source with C/N ratio of 10/4, pH 7.0 and 28°C. BS-L1011 exhibited a low critical micelle concentration (CMC) of 10.5mg/L and was able to reduce the surface tension of water to 25.8±0.1 mN/m. BS-L1011 was stable over a wide range of temperatures, pH values and salt concentrations. The biosurfactant is reported for the first time to accelerate chemical decolorization of Congo red by sodium hypochlorite, and biological decolorization of Amaranth by Bacillus circulans BWL1061, thus showing a potential in the treatment of dyeing wastewater.
Keywords: Azo dye; Biosurfactant; Decolorization; Pseudomonas taiwanensis; Surface tension.
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