The effect of Ralstonia pickettii addition on methylene blue dye biodecolorization by brown-rot fungus Gloeophyllum trabeum

Methylene Blue (MB) is a thiazine group dye frequently used in the textile industry but the difficulty in degrading its molecule poses a significant risk of toxicity to humans. Gloeophyllum trabeum, a brown-rot fungus, has been previously shown to degrade MB. However, the decolorization capacity achieved was relatively poor due to the extended incubation time. This study aimed to improve the MB degradation process by G. trabeum with the addition of Ralstonia pickettii bacteria. The concentrations of R. pickettii added included 2, 4, 6, 8, and 10 mL (1 mL ≈ 1.39 × 10⁸ CFU), while the degradation process was conducted at 30 °C within a 7-day incubation period. The results showed that the highest decolorization percentage was obtained with the addition of 10 mL R. pickettii. The mixed cultures decolorized MB by approximately 85%, while G. trabeum achieved 11% decolorization. The metabolite product produced from the process included C₁₂H₁₃N₃O₆, C₁₄H₁₄N₃S, C₁₂H₁₁N₃SO₆, C₁₂H₁₁N₃SO₇, and C₂₂H₁₅N₃SO₅. Therefore, it was concluded that R. pickettii could enhance the capability of G. trabeum to decolorize MB.