Combined Effects of Low-Density Polyethylene (LDPE), Zn(II), Cu(II), and Metolachlor on Trichoderma harzianum Growth, Oxidative Stress Induction, and Herbicide Degradation

The widespread presence of microplastics (MPs), heavy metals, and herbicide residues in agricultural soil raises concerns about their combined effects on soil microorganisms. This study examined the combined impact of Zn(II)/Cu(II), low-density polyethylene (LDPE), and metolachlor (MET) on Trichoderma harzianum IM 7002, a strain isolated from heavily polluted soil in central Poland. Exposure to LDPE and MET alone reduced fungal growth and induced oxidative stress, whereas Zn(II) at a concentration of 5 mM and Cu(II) at a concentration of 2.5 mM stimulated growth and enhanced MET degradation. HPLC MS/MS analysis identified transformation products, confirming active degradation even under co-exposure to LDPE and metals. Notably, simultaneous exposure to MET, LDPE, and Cu(II) (5 mM) increased antioxidant enzyme activity and decreased lipid peroxidation, suggesting a strengthened antioxidant defense and/or partial utilization of reactive oxygen species during MET biotransformation. Pollutant mixtures also caused quantitative shifts in membrane phospholipid composition and a slight increase in membrane permeability, indicating both toxic effects and adaptive membrane remodeling in response to chemical stress. Overall, T. harzianum IM 7002 exhibited high tolerance to complex pollutant mixtures while maintaining herbicide-degradation capacity, highlighting its potential for remediation of contaminated agricultural soils.