Performance of a newly isolated salt-tolerant yeast strain Pichia occidentalis G1 for degrading and detoxifying azo dyes

A salt-tolerant yeast named G1 which could decolorize various azo dyes was recently isolated and identified as Pichia occidentalis. Systematic researches on characterization, degradation pathway, detoxification effects and enzymes analysis of this yeast were done. The results showed that the optimal metabolism and growth parameters for strain G1 were: 2.0 g L−1 glucose, 0.6 g L−1 ammonium sulfate, 0.08 g L−1 yeast extract, 30 g L−1 NaCl, 160 r min−1, 30 °C and pH 5.0. More than 98% of 50 mg L−1 Acid Red B (ARB) could be decolorized within 16 h under the optimal conditions. Additionally, strain G1 degraded and obviously detoxified ARB through a possible pathway successively consisting of decolorization, deamination/desulfonation and TCA cycle processes. Moreover, NADH-DCIP reductase was estimated as the key reductase for decolorization and ligninases including lignin peroxidase, manganese peroxidase and laccase were important oxidoreductases for further degradation of decolorization intermediates.