Evaluation of ligninolytic activity in spent mushroom substrate from four cultivated mushrooms

Spent mushroom substrate (SMS) is an abundant residue generated by the mushroom industry, which is mostly discarded. In this study, the SMS of four cultivated mushrooms were evaluated as potential sources of ligninolytic enzymes. Pleurotus ostreatus, P. eryngii, P. djamor and Ganoderma lucidum were cultivated in two different substrates to determine growth, mushroom yields and ligninolytic activity of laccase (Lac) and manganese peroxidase (MnP). Maximum activities in the SMS were 3.731 U/g Lac and 0.191 U/g MnP, both for P. eryngii. Colonized mushroom substrates were also analyzed, and higher activities were found in almost all samples. A correlation test between mushroom yields and ligninolytic activities of each culture was made, and we found that high enzymatic activity in the substrate did not result in high mushroom productivity or vice versa. The SMS was a good source of ligninolytic enzymes. Enzymatic activity depended on the mushroom species and its affinity to the substrate, and it was not influenced by the mushroom yields. Production of mushrooms in diverse lignocellulosic substrates is gaining interest, and obtaining ligninolytic enzymes from residual SMS is an excellent alternative in the circular economy concept.