| Summary: | 碩士 === 東海大學 === 食品科學系 === 102 === Inonotus obliquus is a kind of mushroom which has long been used as a folk remedy for curing various diseases such as cancers, heart disease and diabetes in Russian and Eastern Europe. Exopolysaccharides (EPS) are one of the main bioactive constituents of I. obliquus with health functions and many kinds of EPS-related health supplements have been developed in the market. A EPS-producing I. obliquus, was selected in this research to study the effect of submerged culturing condition and different types of fermentors on the production and bioactivity (antioxidative activities, molecular weights and β-(1→3)-D-glucan content) of EPS by this strain.Results showed that Inonotus obliquus had a mycelial growth rate of 0.32 cm/day on basal medium agar at 30℃. Factors for optimal submerged-culturing condition were : glucose at 1% (w/v), peptone at 1% (w/v), corn steep liquor at 0.3% (w/v), MgSO4．7H2O at 0.1% (w/v) , initial pH of 8.0 and inoculum of 10% (v/v). Under this optimized culturing condition, maximal yields of mycelial biomass (6.28 g/l) and EPS (191.57 mg/l) were reached on the 10th day of incubation from shake flask culture and increased 1.68 and 1.88 times, respectively, as compared with those (3.74 g/l and 101.63 mg/l) of the basal medium.The highest biomass yield (Xmax=6.28 g/l) and biomass formation rate (Qx=0.63 g/l/day) were observed from shake flask culture. Among the three types of fermentors, both maximal exopolysaccharide yield (Pmax) and maximal biomass yield (Xmax) showed an increasing tendency of air lift fermentor > stirred-tank fermentor > bubble column fermentor.The molecular weight of exopolysaccharides from shake flask and three types of fermentors ranged from 15.96 to 25.7 (×104 Da) .The hot-water extracts of fermented culture from air lift fermentor shwed the highest total antioxidant capacity (IC50=2.41 g/l), ferrous-ion chelating ability (IC50=5.98 g/l) and reducing power (IC50=14.36 g/l) among all extracts from three types of fermentors. The highest DPPH．scavenging effect (IC50=5.43 g/l) was found in ethanolic extract of fermented culture from air lift fermentor.The EPS from air lift fermentor had the highest relative β-(1→3)-D-glucan content among those from three types of fermentors.As mentioned above, using air lift fermentor, which has lower shearing force, better circulating effect and lower temperature injury as compared with stirred-tank and bubble column fermentors, could produce higher yield of EPS from Inonotus obliquus with better bioactivity.
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