The effect of addition of bacterium Pseudomonas aeruginosa on biodegradation of methyl orange dye by brown-rot fungus Gloeophyllum trabeum

The methyl orange (MO), one of common textile dyes from azo groups, has negative impact in human life and the environment. Therefore, many attempts have been devoted to find the most effective method for MO degradation. Brown-rot fungus Gloeophyllum trabeum has identified as the biodegradable agent of MO, but its efficiency is still low, and it requires a long incubation time. In this work, the biodegradable performance of brown-rot fungus Gloeophyllum trabeum was investigated for MO degradation in the presence of bacterium Pseudomonas aeruginosa with various volumes (2-10 mL, 1 mL = 5.05 x 10¹² Colony Forming Unit (CFU)). The addition of 10 mL of bacteria into G. trabeum culture showed the maximum degradation of 88.67% in potato dextrose broth (PDB) medium for the 7-day incubation. The identified metabolites were 4-[((4-dimethyliminio) cyclohexa-2,5-dien-1-ylidene) hydrazinyl] phenolate (C14H15N3O, compound 1), 4-[(4-iminio-cyclohexa-2,5-dien-1-ylidene) hydrazinyl] benzenesulfonate (C12H10N3O3S, compound 2), 4-[(hydroxy-4-iminio-cyclohexa-2,5-dien-1-ylidene) hydrazinyl] benzenesulfonate (C12H10N3O4S, compound 3), 4-[((4-dimethyliminio)-hydroxy-cyclohexa-2,5-dien-1-ylidene) hydrazinyl] methoxy benzenesulfonate (C15H16N3O5S, compound 4), and 4-[((4-dimethyliminio)-dihydroxy-cyclohexa-2,5-dien-1-ylidene) hydrazinyl] dimethoxy benzenesulfonate (C16H18N3O7S, compound 5). Based on the identification of metabolic products, the mixed cultures transformed MO via three pathways: (1) desulfonylation, (2) demethylation, and (3) hydroxylation. These results indicate that P. aeruginosa can enhance MO biodecolorization by G. trabeum.