Biological Degradation of Spent Coffee Grounds by White Rot Fungi

Spent coffee grounds (SCG) are extensively generated as a byproduct of coffee production and consumption. Improper disposal of SCG contributes to greenhouse gas emissions, environmental pollution, and the loss of valuable resources when landfilled or discharged into sewage systems. In response, this study investigates the biodegradation potential of SCG using selected wood-decay fungi known for their ability to secrete a wide spectrum of lignocellulose-degrading enzymes and degrade complex organic compounds. White rot fungi, such as Irpex lacteus, Pleurotus dryinus, and Trametes versicolor, were cultivated in SCG-containing media to evaluate the degradation efficiency, fermentable sugar dynamics, and fungal enzyme secretion patterns. All tested fungi were able to metabolize SCG and exhibited active enzyme secretion during cultivation. P. dryinus and T. versicolor efficiently secreted both cellulases and laccases, with T. versicolor demonstrating laccase activity of 721.193 ± 41.72 U/L, indicating high oxidative potential. Fungal cultivation and enzyme production resulted in a significant carbohydrate degradation in SCG. The most significant decrease was observed in P. dryinus, which achieved a 43.32% reduction in SCG carbohydrates, while T. versicolor and I. lacteus ensured reductions of 39.07% and 35.55%, respectively. The findings demonstrate that SCG can serve as a low-cost substrate for fungal enzyme production, particularly for laccase generation by T. versicolor, while simultaneously enabling SCG biomass degradation. Together, the study shows the potential of white rot fungi for the biological treatment of SCG, contributing to the development of more sustainable strategies for coffee waste valorization as an alternative to environmentally harmful disposal routes.