Methylene Blue biodecolorization and biodegradation by immobilized mixed cultures of Trichoderma viride and Ralstonia pickettii into SA-PVA-Bentonite matrix

Abstract

The problem of industrial dye wastewater poses a critical environmental challenge that demands urgent attention. This is because the direct release of synthetic dyes such as Methylene Blue (MB) into water bodies has been found to have adverse effects on the environment. Therefore, this study aimed to propose immobilization of a mixed Trichoderma viride and Ralstonia pickettii culture into Sodium alginate–Polyvinyl Alcohol-Bentonite (SA-PVA-Bentonite) matrix as a development method for MB decolorization and degradation. Immobilization process was carried out using the entrapment method, where bacteria and fungi cells were homogenized into the SA-PVA-Bentonite matrix. The results showed that immobilized culture (IMO Mix) outperformed the free cells in Mineral Salt Medium (MSM), achieving an impressive 97.88% decolorization rate for 48 h at 30 °C. Furthermore, a total of 3 metabolite product degradation were produced including Azure A and C, as well as Thionine by LCMS analysis. SEM-EDX analysis confirmed that culture was agglomerated within the SA-PVA-Bentonite matrix, while FTIR demonstrated the functional groups of the synthesized beads. Meanwhile, the difference in charge of bentonite facilitated the adsorption of MB onto the beads, and mixed culture supported the degradation process. This study presented a potential solution to environmental problems, particularly those related to the industrial sector. Further analysis was required to address the challenges associated with other industrial dye waste.