Co-Substrating of Peanut Shells with Cornstalks Enhances Biodegradation by Pleurotus ostreatus

Abstract

World consumption of peanuts has increased tremendously, resulting in abundance of peanut shell waste. The high lignin content of peanut shells limits their bioconversion to useful products or recycling. Therefore, the synergy in co-substrating peanut shells (PS) and cornstalks (CS) to enhance biodegradation was evaluated. Various compositions of peanut shells and cornstalks (% dry weight) herein called co-substrate - 90PS:10CS, 75PS:25CS, 50PS:50CS, 25PS:75CS, 10PS:90CS, and two controls Cont1-100PS and Cont2-100CS were studied under solid state fermentation (SSF) with a white rot fungus, Pleurotus ostreatus for 120 days. A two-factorial experiment in a completely randomized design (CRD) was used. Results showed that substrate composition and fermentation time were important variables in substrate degradation. Lignin degradation, losses in organic matter, cellulose and hemicellulose increased with time. Increasing the composition of CS in co-substrates resulted in higher lignin loss. The most lignin (40.6%) was lost in co-substrates with 75-90% CS whereas more organic matter was lost in co-substrate containing 50% CS and above. Highest losses in organic matter (24.09%), cellulose (17.41%), and hemicellulose (52.07%) occurred in co-substrate with 50% CS, which is where the greatest reduction in C:N ratio (33%) also occurred. The macro- and micro-element content of co-substrates and the controls varied and increased significantly after fermentation. Co-substrating PS and CS appears to be a promising, environmentally-friendly approach for bioconversion of both agricultural wastes into bio-products with potential application in animal feed, biofuel, or for cultivation of mushrooms.