LIGNOCELLULOSIC SUBSTRATES DEGRADATION AND in vitro BIOGAS PRODUCTION BY SOLID FERMENTATION WITH Pleurotus ostreatus

Abstract

Agricultural residues and hay pastures with more than 150 d of regrowth are characterized by their high fiber content;  Pleurotus ostreatus digests lignin, cellulose and hemicellulose. The  hypothesis of this study was that Pleurotus ostreatus improves the chemical characteristics and nutritional value of crop residues and pasture for animal feeding. The objective was to determine the chemical characteristics of nutritional value, biogas production and in vitro degradation of corn stubble and mulatto grass (Brachiaria hybrid) treated with the MR and P15 strains of P. ostreatus for 15 and 30 d in solid fermentation. The strains were reactivated on potato dextrose agar medium, and propagated on sorghum. In an Erlenmeyer flask, 50 g of sterile substrate (80% humidity) and 5% inoculum were placed and fermented for 15 and 30 days. At the end, we determined the chemical characteristics of nutritional value, and estimated the production of biogas and methane (CH₄), and the degradation of dry matter (DMS) and neutral detergent fiber (DFDN). The experimental design was completely randomized with a 2³ factorial arrangement. The corn stubble ferments at 30 d presented higher crude protein content. The lowest neutral detergent fiber (FDN) content was found in corn stubble with any strain. Corn stubble with P15 reduced more acid detergent fiber (FDA) than MR. The ferment of 30 d showed higher FDA in the evaluated substrates. Mulatto grass with MR strain produced more accumulated biogas than with P15. Ferments of 30 d produced more accumulated biogas than those of 15 d (p≤0.05). Neither the substrates nor the strains showed differences in the production of accumulated CH₄ (p>0.05). The 30 d ferments with any strain in corn stubble showed higher DMS and DFDN (p≤0.05). Pleurotus ostreatus improved the nutrient content and the in vitro fermentative characteristics of corn stubble and mulatto grass treated using solid fermentation.