Microbial Synergy: Fungal Laccase-Mediated Optimized Bio-detoxification and Extremophile-Driven Bio-devulcanization of Ground Tire Rubber for Sustainable Recycling

The accumulation of waste tires globally facades a serious environmental challenge necessitating feasible and economic recycling solutions. Unfortunately, tire rubber chemicals cause growth inhibition of rubber remediating bacterium Acidothiobacillus ferrooxidans. This study highlights a dual-stage optimized process involving ground tire rubber (GTR) bio-detoxification using crude laccase harnessed from white rot fungus (WRF) Resinicium bicolor , prior to bacterial bio-devulcanization. Preliminary optimization of laccase production was carried out using a one-factor-at-a-time (OFAT) approach, and the molecular weight of the produced enzyme was subsequently verified by SDS–PAGE analysis. Optimization via Response surface methodology (RSM) enhanced bio-detoxification efficiency to 98.5% being 1.5-fold higher than non-optimized conditions. ATR-FTIR analysis revealed structural modification of bio-detoxified (BD _T ) - GTR, confirming laccase-mediated chemical alterations. Subsequently, bio-devulcanization (BD _V ) displayed A. ferrooxidans superior growth on BD _T -GTR against non-detoxified (ND _T )-GTR and thus validated efficacious detoxification. ATR-FTIR analysis revealed the formation of sulfoxide functional groups following BDV treatment, confirming sulfur oxidation. Concurrently, sulfate concentrations increased to 1.84 g/L in NDT-GTR within 8 days and reached 1.95 g/L in BDT-GTR after 20 days of incubation. Furthermore, scanning electron microscopy coupled with energy-dispersive X-ray (SEM-EDX) analysis indicated modifications in elemental composition, with sulfur content decreasing from 1.3% to 0.9% and a notable emergence of iron, rising from 0% to 2%. Thus, laccase pre-treatment substantially enhances bacterial efficiency and integration of fungal enzymatic detoxification and bacterial sulfur removal allows effective GTR recycling, recommending an eco-friendly strategy for tire waste management.