| Summary: | 碩士 === 東海大學 === 食品科學系 === 98 === Phellinus linteus is a precious medicinal mushroom. The exopolysaccharides (EPS) from P. linteus have been reported to possess important biological functions including anti-tumor, immuno-stimulating, hypoglycemic and antioxidative capacities. Accordingly, many kinds of P. linteus-related EPS products were developed as health foods in the market. A EPS-producing P. linteus was selected in this research to study the effect of submerged culturing condition and different types of fermentors on the production and bioactivity (molecular weight, relative β-(1→3)-D-glucan content, antimicrobial and antioxidative activities) of EPS by this strain.
Results showed that Phellinus linteus HS-050614D-02 had mycelial growth rate of 0.76 cm/day on basal medium agar. The factors for optimal submerged-culturing condition were : incubation temperature of 30℃, fructose at 1% (w/v), yeast extract at 1% (w/v), corn steep liquor at 0.3% (w/v), MgSO4 at 0.1% (w/v) , initial pH of 5.8 and a C/N ratio (fructose / yeast extract) of 1.0. Under this optimized culturing condition, maximal production of mycelial biomass (9.25 g/l) and EPS (1.99 g/l) were reached on the 12th day and 8th day, respectively, of incubation from shake flask culture and increased 2.69 and 3.44 times, respectively, as compared with those from basal medium .
Among the three types of fermentors, the stirred-tank fermentor showed the highest specific growth rate (μ = 0.62 day-1) and specific product yield (Yp/x = 61.51 mg/g). The air lift fermentor showed the highest biomass formation rate (Qx = 0.77 g/l/day) and product formation rate (QP = 0.39 g/l/day). As for biomass yield (Yx/s) and product yield (Yp/s), results showed an increasing tendency of air lift fermentor > air bubble fermentor > stirred-tank fermentor.
Same molecular weight (~3000 Da) was found in EPS from the shake flask and three different types of fermentors. The EPS from culture of air lift fermentor had higher content of molecular weight of 2797 Da.
The EPS of P. linteus PL02 demonstrated no antibacterial activities against the six bacterial strains (Bacillus cereus BCRC 10250, Escherichia coli BCRC 10239, Listeria monocytogene BCRC 14845, Pseudomonas aeruginosa BCRC 10261, Staphylococcus aureus BCRC 10451 and Salmonella typhimurium BCRC 10241) tested.
Under same concentration (10 g/l), the fermented cultures from air lift fermentor showed the highest DPPH scavenging effect ( IC50 = 5.35 g/l), total antioxidant capacity (IC50 = 2.04 g/l) and reducing power (IC50 = 3.12 g/l) respectively, among those from shake flask and three different types of fermentors. The EPS from air bubble and air lift fermentors also had higher relative β-(1→3)-D-glucan contents of 16.25 and 15.83 μg/ml LE, respectively.
As mentioned above, using air lift fermentor, which has lower shearing force and better circulating effect as compared with stirred-tank and air bubble fermentors, could produce higher production of EPS from Phellinus linteus PL02 with better bioactivity.
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