Phorbol ester biodegradation in Jatropha curcas cake and potential as a substrate for enzyme and Pleurotus pulmonarius edible mushroom production

Abstract

Jatropha curcas is a model for biorefinery applications. Although J. curcas cake (JCC), a product of oil extraction, shows potential in animal feed, inactivation of toxic phorbol esters (PE) in residues is necessary. Biological detoxification offers promise for animal feed, as well as for edible mushroom and enzyme production. Here, strains of Aurantioporus pulcherrimus, Ganoderma lucidum, Agaricus sp., Agaricus fuscofibrillosus, Agaricus mediofuscus, Ascopolyporus sp., Panaeolus antillarum, Lentinus strigellus, Amylosporus sp. and Pleurotus pulmonarius were screened for degradation of PE in JCC. These selected macrofungi degraded PE in solid culture over a 30-day period at 28 °C. Among the evaluated basidiomycetes, P. pulmonarius displayed the highest rate of PE degradation, reaching 97% efficiency. To induce the formation of fruiting bodies, P. pulmonarius was further cultivated over 60 days in JCC and five different JCC formulations, each supplemented with an additional lignocellulosic source, with up to a 99.5% degradation of the toxic compound achieved. Fungal fruiting was observed in four of the formulations tested. Biological efficiency (BE) reached 25% in a formulation of JCC plus sawdust. Ligninases, cellulases, hemicellulases, proteases, phytases, esterases and lipase activities were quantified from crude extracts of Spent Mushroom Substrate (SMS) from this formulation. Bromatological analyses here also revealed increases in protein content, Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), cellulose and hemicellulose, and a reduction in dry matter, lignin, and ethereal extract. In conclusion, P. pulmonarius was efficient in degradation of PE in JCC, with the residue appropriate for animal feed input, for production of edible mushrooms, and as a source of enzymes of biotechnological interest.