碩士 / 明新科技大學 / 化學工程研究所 / 96 / Abstract
Armillariella mellea is one of the fungi food-medicine mushroom with tranquilizing central nervous and reducing death rate of mice inducing by nicotine. Simultaneously, it can treat for dizziness, palsy, insomnia, tinnitus, etc. Many researchers demonstrate that A. mellea polysaccharide has excellent anti-tumor activity. The purpose of this study is to optimize the submerged culture conditions to produce the mycelial growth product and the exopolysaccharide by Armillaria mellea with respect to several operating parameters in shake flask fermentation. The experimental results exhibited that the optimal conditions, glucose and yeast extract were the most suitable carbon and nitrogen sources for mycelial growth and EPS production, respectively. The most suitable carbon and nitrogen source concentrations for mycelial growth and EPS production were 40 g L-1 glucose and 3 g L-1 yeast extract, respectively. The optimal temperature, initial pH and trace element for mycelial growth and EPS production by Armillaria mellea in shake flask cultures were found to be 22℃, 4.0 and MgSO4, respectively. The optimal MgSO4 concentration is 2 g L-1. The optimal conditions obtained from the study can be used in submerged culture of A.mellea to promote mycelial growth and EPS production. Under this condition in a 5-L stirred-tank fermenter culture, the maximum EPS production was 588.30 mg L-1. In the optimized medium, the EPS production was 82.20% higher than that at basal medium in a fermenter culture. In addition, the fermentation product extracts (i.e. methanolic extract from mycelia, exopolysaccharide from broth, methanolic extract from broth, hot water extract from mycelia and intracellular polysaccharide from mycelia) showed high antioxidant activity, reducing powers, scavenging effects on 1,1-diphenol-2-picrylhydrazyl radicals, chelating effects and scavenging effects on superoxide anion. The lowest EC50 values for antioxidant activity were 3.45 mg mL-1, 0.73 mg mL-1 for reducing powers, 2.96 mg mL-1 for scavenging effects on 1,1-diphenol-2-picrylhydrazyl radicals, 0.12 mg mL-1 for chelating effects and 0.51 mg mL-1 for scavenging effects on super oxide anion. Due to all EC50 below 10 mg mL-1, the polysaccharide produced by Armillaria mellea possess a great potential in developing antioxidant health-foods. In this study, molecular weight and protein content of exopolysaccharide and antioxidant compounds from fermentation product extracts were also tested, and the results indicated that the key compound of hot water extract from mycelia mainly compound was total phenols (30.90 mg g-1). The number average molecular weight of exopolysaccharide was 7.99×106 (Da), and protein content of EPS was about 7.68 %.
Effects of the different pH on cell growth and exopolysaccharides production by submerged culture of Armillaria mellea were also examined in 5-L stirred-tank fermenter cultures. The results showed that the maximum specific growth rate (μ) was 0.27 d-1 at pH 4 control. At pH 5 control, maximum values of the biomass concentration and productivity for biomass (QX) were 14.59 g L-1 and 1.46 g L-1d-1, respectively. At pH 4 control, maximum values of the EPS concentration and productivity for EPS (QP) were 562.01mg L-1 and 56.20 mg L-1d-1, respectively. For antioxidant activity test of EPS obtained from fermentation of Armillaria mellea at different pH, the maximum antioxidant activity (40.65%) and scavenging DPPH effect (47.77%) of EPS (500ppm) occurred at pH 4 and pH 5, respectively. Mw of EPS from different pH cultures by Armillaria mellea was ranged from 4.76×106 ~ 6.99×106 Da. Mw of EPS from sudmerged culture at lower pH range (pH 3 ~ 4) is more than that of higher pH range (pH 5 ~ 7). The maximum protein / polysaccharide (%) of EPS from sudmerged culture at pH 5 control (6.62%). Protein / polysaccharide (%) was related highly to scavenging DPPH effect (R2 = 0.91). The DPPH scavenging activity increases with protein / polysaccharide (%). The results indicated that the optimal culture condition for EPS with maximum antioxidant activity is at pH 4;and maximum scavenging DPPH effect is at pH 5.
Keywords: Armillaria mellea , Exopolysaccharide ,Optimal, Antioxidant, pH
| Identifer | oai:union.ndltd.org:TW/096MHIT5062018 |
| Date | January 2008 |
| Creators | 張祐誠 |
| Contributors | 龍明有 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 141 |
Page generated in 0.1997 seconds