Polysaccharides production from soybean curd residue via Morchella esculenta

To minimize the serious environmental pollution caused by food byproducts, soybean curd residue was used as the substrate to ferment polysaccharides by Morchella esculenta. Water-soluble crude polysaccharides (CMP) were purified by different gradient concentrations (30%, 60%, and 90%) of ethanol into three precipitation fractions. The experimental results indicated that the precipitated polysaccharides by the ethanol concentration of 60% (PMP) had the highest purity, containing rhamnose, arabinose, xylose, mannose, glucose, and galactose, with the molar ratio of 0.08:0.25:0.16:0.07:0.28:1.00. The physicochemical properties were revealed by SEM, AFM, FTIR, NMR, and Congo red test. Furthermore, the measurement of antioxidant activities in vitro demonstrated that PMP exhibited higher antioxidant capacities with the dose-dependent manner than CMP and polysaccharides from unfermented soybean curd (USP). Overall, the results suggested that PMP had attractive functional activity which could be potentially utilized in functional food industries. Practical applications The polysaccharides from fungi sources are increasingly being used in functional food and pharmaceutical industry. In allusion to the problem of polysaccharides fermented by edible fungi, such as low yield, high cost, and hard to controllable. Soybean curd residue (SCR), a food waste, has been successfully used for the production of polysaccharides and graded ethanol was used to enhance polysaccharides production, lower the difficulty and homologous costs of purity. The results indicated that the purified polysaccharides displayed excellent antioxidant activities on scavenging DPPH and hydroxyl radicals. The outcomes of this work can provide technical support for comprehensive utilization of SCR and references for promotion and application of polysaccharides fermented from SCR via Morchella esculenta in food and medicine fields.