Bioremediation of malachite green dye toxicity under optimized conditions by Rhodotorula mucilaginosa AUMC13567

The escalating impacts of human urbanization and rapid industrial development have resulted in a growing global demand for synthetic textile dyes. Malachite green (MG) dye is a hazardous chromatic compound predominantly utilized as a textile dye, exhibiting a strong affinity for the substrate to which it is applied. When diluted, it serves as antimicrobial agent for fungal and bacterial diseases in fish farms. However, the disposal of textile dyeing wastes pose significant environmental challenges, contaminating soil, surface water, and adversely affecting human health and aquatic life. R. mucilaginosa exhibits robust growth and resistance capabilities even under conditions of nutrient deficiency or external stress. This study focuses on optimizing the malachite green dye degradation ability of the yeast strain Rhodotorula mucilaginosa AUMC13567. The results reveal that the optimal conditions for maximum decolorization which was 100% at 50 mg/L dye concentration involve cultivating R. mucilaginosa on medium comprising distilled water with 3% glucose, 0.5% peptone, 0.3% malt extract, and 0.3% yeast extract under aerobic conditions at 37˚C for 12 h at 150 rpm. Gas Chromatography-Mass Spectrometry (GC/MS) analysis confirms the yeast's efficacy in degrading toxic MG dye complex compounds into simple harmless metabolites. Fourier Transform Infrared (FTIR) analyses show formation of novel compounds post the degradation of MG dye. Further research is advised to identify and characterize the specific enzymes or metabolic pathways implicated in MG dye degradation by R. mucilaginosa AUMC13567. Cytotoxicity tests carried out on three human cell lines, including colorectal cancer, head and neck cancer, and healthy skin fibroblast, demonstrating that decolorized MG solution produces safe products devoid of cytotoxicity on tested human cell lines.