Rapid lignin degradation and reusability of a chitosan-immobilized fungal consortium: a comparative evaluation with the suspended system

Lignin-rich effluents generated from kraft pulp mills are difficult to treat because of the recalcitrant aromatic structure of lignin. Although fungal consortia can enhance lignin degradation through synergistic enzymatic activity, suspended systems often suffer from poor operational stability and limited reusability. Therefore, this study aimed to develop a novel fungal consortium comprising newly isolated Penicillium spp. and Leiotrametes flavida (MTCC 12927) for lignin degradation, investigate different immobilization matrices to identify a suitable support system, and evaluate the effect of immobilization on degradation efficiency, extracellular enzyme activity, operational stability, and reusability. The lignin degradation performance of the consortium was first evaluated using a model lignin-rich wastewater (lignin concentration of 1 g L − 1 ) under suspended conditions, followed by screening of different immobilization matrices and assessment of the effects of immobilization on degradation efficiency, enzyme activity, operational stability and reusability. Among the designed consortia, consortium C3, comprising Penicillium spp. AP1, Penicillium spp. AP2, and Leiotrametes flavida AP3 mixed in a volumetric ratio (v/v) of 3:1:2, exhibited the highest lignin degradation efficiency. Under optimized conditions, the suspended consortium degraded 86.27% lignin in 24 h, whereas the immobilized consortium achieved 97.5 ± 0.42% degradation in 24 h, with 97.1 ± 0.8% degradation attained within 6 h. The immobilized consortium retained > 80% degradation efficiency for 12 consecutive cycles, indicating excellent operational stability and reusability. Among the ligninolytic enzymes, manganese peroxidase (MnP) showed the highest activity, reaching 1925.1 ± 7.2 U mL⁻¹ in the suspended consortium and 592.7 ± 9.5 U mL⁻¹ in the immobilized consortium. Treatment also reduced COD (96.8%) and BOD (79.7%). Overall, chitosan immobilization enabled rapid, reusable, and highly efficient lignin degradation, demonstrating strong potential for treatment of lignin-rich industrial wastewater.