Valorization of Paddy Straw Using De-oiled Cakes for P. ostreatus Cultivation and Utilization of Spent Mushroom Substrate for Biopesticide Development

Abstract

Paddy is widely consumed staple food for the largest part of the world's human population. The disposal of paddy straw (PS) is causing worldwide environmental concern. Although, the utilization of PS for mushroom cultivation is well known, it’s amendment with nutrient rich substances to yield quality nutraceutical mushrooms along with value addition of spent may increase its consumption many folds. In the present study, Pleurotus ostreatus was cultivated on PS and comparative analysis on effects of supplementation of different de-oiled cakes on yield, nutritional content and antioxidant properties of mushroom were investigated. Addition of soyabean cake (SC) gave maximum yield of 1014 g kg−1 fruiting bodies, furnishing an increase of 18.14% over PS control. Phenolic content of the fruiting bodies varied in the range of 8.14–11.59 mg GAE g−1. Principle component analysis (PCA) was performed to observe the variation among different treatments by studying the correlation within nutritional parameters (moisture, crude protein, carbohydrates, fat and crude fiber). A total variation of 78.2% was observed by analyzing PC1 and PC2. Energy dispersive X-ray (EDX) analysis indicated significant increase of minerals (Se, K, Zn, Fe, Cu, Ca, P) in the fruiting bodies supplemented with de-oiled cakes and high content of silica in the spent. FTIR studies confirmed the degradation of cellulose (24–33.5%), hemicellulose (15.5–24.2%) and lignin (26.4–36.5%) content in different spent substrates. Further, in an attempt to see the suitability of spent for the growth of Trichoderma asperellum, it was found that growth was comparatively high in SC supplemented PS spent (14.73*1011) over raw PS (4.2*103). In addition to this, T. asperellum grown on supplemented PS showed 66.26% inhibition of Fusarium oxysporum f. sp. lycopersici as compared to the non-supplemented spent (54.26%). High silica (19–20%) and NPK content in mushroom spent envisages the development of Si based formulations having enhanced bio-fertilizer and bio-pesticidal properties.