Fungal pretreatment of rice straw with Pleurotus ostreatus and Trichoderma reesei to enhance methane production under solid-state anaerobic digestion

Rice straw was subjected to fungal pretreatment using Pleurotus ostreatus and Trichoderma reesei to improve its biodegradability and methane production via solid-state anaerobic digestion (SS-AD). Effects of moisture content (65%, 75% and 85%), and incubation time (10, 20 and 30 d) on lignin, cellulose, and hemicellulose degradation during fungal pretreatment and methane yield during anaerobic digestion were assessed via comparison to untreated rice straw. Pretreatment with P. ostreatus was most effective at 75% moisture content and 20 d incubation resulting in 33.4% lignin removal and a lignin/cellulose removal ratio (selectivity) of 4.2. In comparison Trichoderma reesei was most effective at 75% moisture content and 20 d incubation resulting in 23.6% lignin removal and a lignin/cellulose removal ratio (selectivity) of 2.88. The corresponding methane yields were 263 and 214 L/kg volatile solids (VS), which were 120% and 78.3% higher than for the untreated rice straw, respectively.