High-Level Production of Exopolysaccharides by a Cosmic Radiation-Induced Mutant M270 of the Maitake Medicinal Mushroom, Grifola frondosa (Agaricomycetes).

A new Grifola frondosa mutant, M270, was successfully isolated for high production of exopolysaccharides (EPSs) using cosmic radiation-induced mutagenesis. We found that the mutant M270 had a clearer and thicker EPS layer (~10 µm) adhering to mycelia than those of its parent strain 265 after Congo red staining. In the 20-L batch fermentation for M270, 10.3 g/L of EPS and 17.9 g/L of dry mycelia biomass were obtained after 204 hours of fermentation. Furthermore, a main water-soluble fraction (EP1) in the EPS was purified from M270 and then confirmed to be heteroglycan-protein complex with 91% (w/w) total carbohydrates and 9% (w/w) total proteins. Four kinds of monosaccharide-D-mannose, D-glucosamine, D-glucose, and D-xylose-were detected in EP1 with a molar ratio of 17.6:1.8:100:2.5. The molecular mass of the main component in EP1 was 8.9 kDa. The EPS from M270 significantly inhibited the growth of sarcoma 180 solid tumors in mice. This G. frondosa M270 mutant could serve as a better candidate strain for polysaccharide production.

[The protective effects of insulin on cardiocyte apoptosis challenged by burn serum].

OBJECTIVE: To investigate the protective effects of insulin on burn serum-challenged cardiocyte apoptosis and its mechanism. METHODS: Burn-serum challenged cardiocytes were pretreated with insulin and inhibitors to pathway SB203580 and LY294002. The expression of cardiac myofilament proteins cleaved-caspase-3, Bax and phosphorylation nuclear factor-ΚB inhibitive factor α (p-IΚBα) were examined by Western blotting. The mRNA expression of tumor necrosis factor-α (TNF-α) was determined by real-time reverse transcription-polymerase chain reaction (RT-PCR). Apoptosis of cardiocyte was observed after Hoechst 33258 staining. Further blocking experiments were used to investigate the cytoprotective pathway of insulin. RESULTS: Insulin could significantly decrease the expression of cleaved-caspase-3 (2.22 ± 0.30 vs. 4.84 ± 0.74, P < 0.01), Bax (1.33 ± 0.35 vs. 3.74 ± 0.65, P < 0.01), p-IΚBα (1.43 ± 0.62 vs. 3.62 ± 0.74, P < 0.01), TNF-α (0.72 ± 0.27 vs. 2.02 ± 0.63, P < 0.01) and the cardiocyte apoptosis rate [(9.4 ± 3.4)% vs. (19.1 ± 5.6)%, P < 0.01] in cardiocytes challenged by burn serum. Further blocking experiments showed that LY294002, phosphatidylinositol-3-kinase (PI3K)/Akt activation inhibitor, could mitigate the protective effects of insulin. Meanwhile, SB203580, an inhibitor of p38 mitogen-activated protein kinase (p38MAPK) pathway, was able to inhibit cardiocyte injury challenged by burn serum, and it was as effective as insulin. CONCLUSION: For cardiocytes challenged by burn serum, insulin may decrease inflammatory cytokine expression and apoptosis via regulating PI3K/Akt and p38MAPK pathway.