Abstract
Humic acid (HA) is natural product obtained by plant decomposition. It improves systematic resistance in plants and the shelf life of food products. Oyster mushrooms occupy important place in human food due to their palatability and nutritional enrichment. Little is known about the impacts of HA on mushrooms yield. Therefore, a trial was conducted to study the role of HA improving growth, nutritional and chemical composition of two oyster mushroom strains (Pleurotus ostreatus, Lentinus sajor-caju). Pure cotton waste amalgamated with five levels of HA, i.e., 2, 4, 6, 8 and 10 mM/L was used as growth media. The responses of oyster mushroom to HA were recorded in various traits i.e. time to spawn initiation, time to mycelium growth initiation, time to maturity of flushes, time to initiation of pinheads, yield, biological efficiency (BE), minerals (N, P, K, and ascorbic acid, Zn, Cu, Mg, Mn, Fe, Na and Ca), sugars (total sugars, reducing and non-reducing sugars), proximate, total soluble solids (TSS), acidity, and Fourier-transform infrared spectroscopy (FTIR). The HA amalgation notably improved the growth, nutritional and chemical composition of oyster mushroom; however, strains differences were non-significant (>0.05) to various level of HA on dry weight basis TSS ranged from 6 to 6.8 degrees Brix, total sugar was 5.8-11.9%, reducing sugar was 2.6-3%, non-reducing sugar was 9.2-9.6%, ascorbic acid was 35.9-43 mg/100 g, carbohydrates were 68-74%, crude protein was 62-69%, crude fiber was 22-37%, fat contents were 2.5-17%, ash content was 9-11%. These results suggest that HA is an innovative substrate for valuable and high-quality production of the oyster mushroom. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of King Saud University.