Anthocyanin extract from Lycium ruthenicum enhanced production of biomass and polysaccharides during submerged fermentation of Agaricus bitorquis (Quél.) Sacc. Chaidam.

Agaricus bitorquis (Quél.) Sacc. Chaidam (ABSC) is a wild edible fungus uniquely found in the Tibet Plateau. ABSC is rich in polysaccharides that are considered biologically active. This study aimed to determine the feasibility of enhancing exopolysaccharide (EPS) production by ABSC in shake flask culture by supplementing the fermentation medium with anthocyanin extract. Different concentrations of Lycium ruthenicum Murr. (LRM) anthocyanin crude extract were tested on ABSC fermentation. The activity of phosphoglucose isomerase (PGI), phosphoglucose mutase (PGM), and phosphomannose isomerase (PMI), enzymes presumably involved in EPS synthesis by ABSC, was determined. ABSC transcriptomic profile in response to the presence of anthocyanins during fermentation was also investigated. LRM anthocyanin crude extract (0.06 mg/mL) was most effective in increasing EPS content and mycelial biomass (by 208.10% and 105.30%, respectively, P < 0.01). The activity of PGI, PGM, and PMI was increased in a medium where LRM anthocyanin extract and its main components (proanthocyanidins and petunia anthocyanin) were added. RNA-Seq analysis showed that 349 genes of ABSC were differentially expressed during fermentation in the medium containing anthocyanin extract of LRM; 93 genes were up-regulated and 256 genes down-regulated. From gene ontology enrichment analysis, differentially expressed genes were mostly assigned to carbohydrate metabolism and signal transduction categories. Collectively, LRM anthocyanins extract positively affected EPS production and mycelial biomass during ABSC fermentation. Our study provides a novel strategy for improving EPS production and mycelial growth during ABSC liquid submerged fermentation.

In Vitro Antioxidant Activities and in Vivo Anti-Hypoxic Activity of the Edible Mushroom Agaricus bisporus (Lange) Sing. Chaidam.

With the rising awareness of a healthy lifestyle, natural functional foods have gained much interest as promising alternatives to synthetic functional drugs. Recently, wild Agaricus bisporus (Lange) Sing. Chaidam has been found and artificially cultivated for its thick fresh body and excellent taste, with its antioxidant and anti-hypoxic abilities unknown. In this work, the antioxidant potential of its methanolic, 55% ethanolic, aqueous extracts and crude polysaccharide was evaluated in different systems. The results showed that polysaccharide was the most effective in scavenging ability on 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals, metal chelating activity and reducing power, with EC50 values of 0.02, 2.79, 1.29, and 1.82 mg/mL, respectively. Therefore, we further studied the anti-hypoxic activity of crude polysaccharide. The results turned out that polysaccharide (300 mg/kg) prolonged the survival time, decreased the blood urea nitrogen and lactic acid content as well as increased the liver glycogen significantly, compared with the blank control and the commercialized product Hongjingtian (p < 0.05). With such excellent activities, we purified the polysaccharide and analyzed its molecular weight (120 kDa) as well as monosaccharide components (glucose, fructose and mannose). This study indicated that wild Agaricus bisporus (Lange) Sing. Chaidam had strong potential to be exploited as an effective natural functional food to relieve oxidative and hypoxia stresses.