Bioremediation and Detoxification of the Textile Dye Methyl Blue by Trichoderma asperellum LBKURCC1 with Laccase Activity

Textile production generates effluent contaminated by 10-15 % dyes used. Fungal-mediated remediation presents an ecologically acceptable and inexpensive method for treating dye effluents. Trichoderma asperellum LBKURCC1 isolated from Riau cacao rhizosphere produces laccase. Laccase can catalyse the degradation of several textile dyes. This study aims to investigate T. asperellum LBKURCC1 ability to bioremediate and to detoxify the textile triphenylmethane dye, methyl blue (MB). T. asperellum LBKURCC1 cultures in minimal media with pHs of 4.5, 5.5 and 6.5 were incubated (24 hours, room temperature) with 50-ppm MB solutions.  MB decolorisation analysis was conducted by examining the UV-Vis absorption spectra of MB after 24 hours treatment. It was also determined if the degradation was contributed by enzymatic biodegradation or by biosorption processes. The contribution of laccase activity to the bioremediation process was assessed by monitoring laccase activity in fungal treated MB solution. Acute toxicity of MB to Artemia salina larvae was determined pre- and post-fungal treatment. The results showed that decolorisation of MB by T. asperellum LBKURCC1 occurred at all tested pH levels, but at different rates for different pH. The highest decolorisation rate was at pH 4.5 (85 % per 24 hours). Enzymatic biodegradation was the higher contributor to the decolorisation, compared to mycelia biosorption. Laccase activity was induced by MB and the highest activity was found at pH 4.5.  MB toxicity to A. salina larvae was eliminated by the fungal biodegradation. This study confirms the potential of T. asperellum LBKURCC1 life cultures in the degradation of MB, eliminating its toxicity.