The effect of Ralstonia pickettii bacterium addition on methylene blue dye biodecolorization by brown-rot fungus Daedalea dickinsii.

Methylene blue (MB) is one of synthetic dyes that is used in the textile industry which is difficult to degrade in nature. Previously, the brown-rot fungus (BRF) Daedalea dickinsii had shown a good ability to degrade MB, however, the decolorization ability was relatively still low and had a long period of incubation. Therefore, improvement of process is needed to increase the ability of D. dickinsii to decolorize MB. In this study, the effect of Ralstonia pickettii bacterium addition on MB biodecolorization by the BRF D. dickinsii in potato dextrose broth (PDB) medium was investigated. The amount of R. picketti that was added to the culture of D. dickinsii were 2, 4, 6, 8, and 10 mL (1 mL ≈ 1.39 × 108 CFU). The cultures had ability to decolorize MB (100 mg/L) at 30 °C after 7 days incubation. The highest percentage of MB biodecolorization was obtained at addition of 10 mL of R. pickettii approximately 89%, while biodecolorization process by particularly D. dickinsii was approximately 17%. The MB degradation metabolites by mixed cultures of D. dickinsii and 10 mL of R. pickettii were Azure A, thionine, glucose-MB, C12H11N3SO6 and C12H13N3O6. This study indicated that the addition of R. pickettii could enhance MB biodecolorization by fungus D. dickinsii. Besides that, this study also indicated that mixed cultures of D. dickinsii and R. pickettii has great potential for high efficiency, fast and cheap dye wastewater treatment.

Biodegradation of Aldrin and Dieldrin by the White-Rot Fungus Pleurotus ostreatus.

Aldrin and its metabolite dieldrin are persistent organic pollutants that contaminate soil in many parts of the world. Given the potential hazards associated with these pollutants, an efficient degradation method is required. In this study, we investigated the ability of Pleurotus ostreatus to transform aldrin as well as dieldrin in pure liquid cultures. This fungus completely eliminated aldrin in potato dextrose broth (PDB) medium during a 14-day incubation period. Dieldrin was detected as the main metabolite, and 9-hydroxylaldrin and 9-hydroxyldieldrin were less abundant metabolites. The proposed route of aldrin biotransformation is initial metabolism by epoxidation, followed by hydroxylation. The fungus was also capable of degrading dieldrin, a recalcitrant metabolite of aldrin. Approximately 3, 9, and 18% of dieldrin were eliminated by P. ostreatus in low-nitrogen, high-nitrogen, and PDB media, respectively, during a 14-day incubation period. 9-Dihydroxydieldrin was detected as a metabolite in the PDB culture, suggesting that the hydroxylation reaction occurred in the epoxide ring. These results indicate that P. ostreatus has potential applications in the transformation of aldrin as well as dieldrin.