Evaluation of the biotechnological potential of the spent mushroom substrate from the cultivation of Pleurotus spp for biogas and enzyme production

PÉREZ CHÁVEZ, M.; ALBERTI, M.; ALBERTÓ E.

Ensenada

Simposio; XV Simposio Internacional de Microbiología Básica y Aplicada; 2022

The species Pleurotus ostreatus, P. eryngii and P. djamor were cultivated following the common practices of industrial fugiculture. Mushrooms were harvested during 4 to 6 weeks and yields were noted. From this results we can assure that the production of edible mushrooms occurred accordingly to what happens in the industry and also we were able to make comparisons with the cultivation of each species in two very different substrates. With the production of edible fungi, significant amounts of organic waste is generated. The residue of the blocks after the cultivation process is finished, is called Spent Mushroom Substrate (SMS). In fact, for every kilogram of mushrooms harvested, approximately 5 kg of SMS is generated, so searching for alternative uses is environmentally necessary. Usually in the industry the SMS is burned in the open or is buried in the fields. The use of SMS directly or as a source of valuable biomaterials is becoming object of investigation, mainly for applications in bioremediation. In this work we explored the use of SMS as an organic source for the production of biogas through anaerobic digestion in 2 L bioreactors under mesophilic conditions. Biogas and biomethane were obtained from this experiments with results not very distant from the ones obtained with the utilization of colonized substrates (substrates with fungi prior the fructification phase). SMS was also used to obtain enzymatic extracts for the quantification of lignocellulolytic activity such as cellulase, laccase and manganese peroxidase. We analyzed spent substrates and colonized substrates in order to compare the amount of enzymes in the two phases of fungal growth (after colonization and after fructification). In all cases we obtained enzymatic activities and we observed activities with no significant differences between SMS and colonized substrate. Finally, we analyzed the use of SMS as a vegetable amendment in seedlings of spinach, cabbage, tomato and lettuce with promising results. Seedlings were able to grow as the control group and the application of SMS seems to be beneficial for the maintenance of the plants for longer periods of time without desiccation. SMS turned out to be a good organic source for our experiments. Production of mushrooms in diverse lignocellulosic substrates is gaining interest, and obtaining byproducts from residual SMS is an excellent alternative within the circular economy concept.