Mixed-species Pseudomonas biofilms: a novel and sustainable strategy for malachite green dye decolorization and detoxification.

This study investigated the application of mixed biofilms formed by two Pseudomonas strains (NAA22 and NAA23) for bio-decolorization of malachite green (MG) dye. The isolated strains displayed biofilm formation and MG decolorization capabilities. Mixed biofilms exhibited significantly greater biofilm formation and MG decolorization (94.3%) compared to individual strains, suggesting synergistic interactions. This decolorization efficiency surpassed previously reported values for single strain decolorization. The mixed biofilms tolerated a broad range of temperatures (20-40 °C) and pH (5-9), with optimal decolorization at neutral or slightly acidic conditions (pH7.0). Enzyme analysis revealed laccase, NADH-DCIP reductase, and azoreductase as key contributors to MG decolorization, with significantly higher activity in mixed biofilms. Importantly, the bio-decolorization process transformed MG into non-phytotoxic compounds, demonstrated by seed germination and growth assays. These findings propose a promising and environmentally safe approach for MG bioremediation using mixed Pseudomonas biofilms.