Effect of edible oils and Cu (II) on the biodegradation of rice by-products by Ganoderma lucidum mushroom

Abstract

The biodegradation of rice agro-industrial residues (straw and husks) to obtain the medicinal white-rot fungi Ganoderma lucidum and a crude extract of laccases as by- product was studied. Mycelium growth analysis on substrate formulations in a solid state fermentation system showed a good growth performance on substrates containing 57–69% straw, 25–30% husk, 5–10% rice bran, and 0–1% olive oil. Total mushroom production of dried mushrooms increased from 2.9% to 3.7% when using 5% vs. 8% mycelium inoculation rates, and from 3.6% to 4.1% when 1% olive oil was added to the substrate formulation. Addition of 100 ppm Cu (II) as a substrate supplement increased laccase activity in mushroom residual substrate from 150 to 267 U/Kg substrate and produced a three-fold increase in mushroom copper content. Extracted laccase activity was stable after four months in freezer storage (−18 °C) and after 16 freezing/thawing cycles.