Integrated bioremediation of microplastics-cadmium co-contamination via chitosan-sugarcane residue encapsulated fungal consortia.

The co-occurrence of microplastics (MPs) and heavy metals in aquatic environments poses a complex challenge for MPs bioremediation, particularly when cadmium (Cd) adsorbs onto MPs surfaces and enhances recalcitrance and microbial stress. This study investigates the biodegradation of MPs based on polyethylene (PE) and polypropylene (PP), under Cd stress using novel fungal consortia (QMFC1 for PE and QMFC2 for PP). To enhance their stability and performance under co-contaminated conditions, both consortia were immobilized in a chitosan-sugarcane residue matrix, resulting in the encapsulated systems C-QMFC1 and C-QMFC2. This study showed that C-QMFC1 and C-QMFC2 exhibited high Cd tolerance and sustained metabolic activity under co-contaminated conditions. Over a 30-day incubation period, the encapsulated system (C-QMFC1 and C-QMFC2) achieved the highest MPs degradation, with PE and PP weight loss reaching up to 53.81% and 39.14%, respectively, significantly exceeding non-encapsulated treatments (QMFC1 and QMFC2). Fungal biomass (0.323-0.374 g) and the activities of key oxidative and hydrolytic enzymes, including catalase (2.02-2.31 U/mL), laccase (1.74-1.92 U/mL), manganese peroxidase (1.85-1.87 U/mL), lipase (1.36-1.47 U/mL), alcohol dehydrogenase (1.45-1.55 U/mL), and aldehyde dehydrogenase (1.43-1.45 U/mL), increased in C-QMFC1 and C-QMFC2 compared with control (Cd-PE and Cd-PP), supporting efficient polymer transformation and coordinated responses to Cd-induced oxidative stress. The scanning electron microscopy showed that C-QMFC1 and C-QMFC2 exhibited extensive surface deterioration. Meanwhile Fourier transform infrared spectroscopy and X-ray diffraction analysis revealed oxidative functionalization and significantly reduced crystallinity, while gas chromatography mass spectrometry detected a range of short-chain alkanes, oxygenated compounds, and fungal metabolites, indicating extensive polymer chain scission and transformation in C-QMFC1 and C-QMFC2. Additionally, the C-QMFC1 and C-QMFC2 demonstrated highest Cd removal efficiencies of 49.0% and 43.4% from the aqueous solution of PE and PP, respectively, with Cd immobilized within the C-QMFC1 and C-QMFC2 systems through adsorption and bioaccumulation. This study demonstrates that C-QMFC1 and C-QMFC2 enhanced fungal resilience, enzymatic efficiency, and remediation performance, offering a robust and eco-friendly strategy for simultaneous MPs degradation and heavy-metal removal in complex co-contaminated aquatic environments.