Mapping of levels of oxidative enzymes in the fruiting bodies of the fungus, Pleurotus ostreatus to different substrates for use as an agent in bioremediation

A significant volume of waste is generated across diverse agricultural sectors and various food industries worldwide. This waste primarily comprises cellulose, hemicellulose, and lignin, collectively called lignocellulosic materials. Sawdust (SD), corn cob (CC), and coconut fibre (CF) can be effectively employed as suitable substrates in the solid-state fermentation process for cultivating mushrooms. Pleurotus ostreatus , through the production of lignocellulosic enzymes, breaks down wastes (substrates) and utilizes the resulting breakdown products to develop their fruiting bodies. By the vigorous growth and biomass generation, they produce potent extracellular enzymes such as lignin peroxidases (LiP), manganese peroxidase (MnP), and laccase capable of eliminating pollutants. The objectives of this investigation were the estimation of the yield of P. ostreatus fruiting bodies and the measurement of levels of lignolytic/oxidative enzymes (lignin peroxidases, manganese peroxidases, laccases) in the fruiting bodies from three substrates. Enzyme extraction and partial purification were conducted to assess the enzymatic activity of P. ostreatus grown on various substrates. Partial purification was achieved by mixing the culture supernatant with ammonium sulphate solution to achieve 80% saturation. Quantitative enzyme assays were performed to measure enzyme activity. One-way ANOVA tests were used to investigate the hypothesis that substrate type affects the activity of the enzymes produced. The results of this study have demonstrated that SD has the highest biological efficiency followed by CC and trailed by CF. Sawdust grows slowly and uniformly, suggesting that it would be an ideal substrate for regular mushroom growth. While corn cobs might provide larger immediate yields, coconut husk may achieve a balance between stability and early yield. Lignin Peroxidase activity is relatively consistent across the three substrates, with only slight variations. SD shows the lowest LiP activity (26.75 ± 1.47 U/L), with CF and CC showing slightly higher but comparable activities ( 30.40 ± 5.00 U/L and 30.87 ± 3.49) respectively. MnP activity is much higher than LiP across all substrates, indicating that this enzyme is more active under the conditions tested. CF has the highest mean MnP activity (596.07 ± 514.59), followed by SD (560.06 ± 204.48U/L) and CC (476.92 ± 480.11 U/L). Laccase activity is much lower compared to LiP and MnP. Activity increases progressively from SD to CF to CC, with CC showing the highest laccase activity (2.44 ± 1.76). The results showed that for laccase and lignin peroxidase, the substrate type significantly increased the activity of the enzymes; however, for manganese peroxidase, the substrate type did not affect its activity, and differences in activity were the result of chance. The findings could help optimize fungal-based treatments for wastewater and other potential pollutants containing toxic compounds, reducing environmental pollution. Additionally, the mapping of enzyme activity can contribute to the selection or genetic improvement of fungal strains with higher bioremediation potential.