| Tremella fuciformis is a traditional edible fungus in China,which is rich in Tremella fuciformis polysaccharide and has many physiological activities such as anti-tumor and anti-aging.In this study,tf526,a target strain with high biomass and exopolysaccharide content,was screened out from three strains of tremella,and the liquid fermentation conditions and decolorization process of exopolysaccharide were optimized.The exopolysaccharide was separated and purified by column chromatography and the in vitro antioxidant experiment was carried out,in order to provide experimental data and theoretical basis for the industrial production of tremella and the antioxidant research of exopolysaccharide.The main experimental results are as follows:(1)Screening of high-yield Tremella mycelia and excellent strainsof extracellular polysaccharide: the target strain Tf526 was screened by comparing the indexes of mycelium biomass and extracellular polysaccharide content.(2)Optimization of the fermentation conditions of Tremella strain Tf526 shake flask: the target strain Tf526 was inoculated with 2% glucose as carbon source,0.4% yeast extract powder as nitrogen source,fermentation temperature 25 ?,initial p H 6.0,150 r/min,8% Under the condition of quantitative liquid culture,the mycelium biomass and extracellular polysaccharide content reached the maximum.The mycelium biomass was 7.4 ± 0.14 g/L,which was an increase of 17.5% compared with that before optimization;the extracellular polysaccharide content of the strain was 0.72±0.03 g/L,which was 30.9% higher than beforeoptimization.(3)The effect of lignocellulase on the mycelium and extracellular polysaccharide content of strain Tf526: The strain YB was identified as Trichoderma virens by morphology and molecular biology and named Trichoderma virens YB.The best carbon source for enzyme production is corn stover powder with a fermentation period of 72 h.During the fermentation process,the maximum activities of cellulase and xylanase were 313.53±26.78 U/mL and 18120.87±500.37 U/mL,respectively.The optimal ammonium sulfate saturation for the preparation of lignocellulase is70%.The lignocellulose complex enzyme with a concentration of 3 mg/mL was added to 10 mL after 60 hours of fermentation,which caused little damage to the mycelium and promoted the secretion of extracellular polysaccharides.The DCW content was 6.8 ± 0.12 mg/mL,and the EPS content was 0.91± 0.05 mg/mL;compared with the blank group(DCW:7.6±0.15 mg/mL,EPS: 0.72±0.03 mg/mL),DCW biomass decreased by10.5%;EPS content increased by 26.4%.Under the optimal fermentation conditions,the white fungus strain Tf526 was expanded and cultured in a fermenter.The mycelium dry weight was 13.26 ± 1.78 g/L,and the extracellular polysaccharide content was 2.03±0.33 g/L.It is 1.79 times the biomass of shake flask fermentation mycelium and 2.82 times of extracellular polysaccharide.(4)Decolorization,deproteinization and impurity removal process of extracellular polysaccharides produced by Tf526 using macroporous resin:The best macroporous resin was selected as A-722 MP,and the adsorption capacity of A-722 MP was used to remove extracellular polysaccharides.The effect of adsorption conditions on the decolorization and deproteinization ability of A-722 MP.The results showed that A-722 MP had the best adsorption conditions(material-liquid ratio 10:1,adsorption temperature 30 ?,adsorption time 2 h).The extracellular crude polysaccharide solution treated with A-722 MP macroporous resin had a decolorization rate of 62.14%,a protein removal rate of 87.8%,and a polysaccharide retention rate of 73.42%.(5)Isolation of extracellular polysaccharide of Tf526 strain and invitro antioxidant experiment: 4 pure polysaccharide components Lf1-a,Lf1-b,Lf2 and Lf3 were isolated from the extracellular polysaccharide of Tf526 strain.Light white flocculent(weight: 1.396 g,0.213 g,0.086 g,0.073 g).And the main components Lf1-a and Lf1-b,in vitro antioxidant experiments,the results show that the total reducing power of Lf1-a component and hydroxyl radical scavenging ability is stronger than the Lf1-b component.When the polysaccharide sample concentration is less than 1.5 mg/mL,the DPPH free radical scavenging ability of Lf1-a is higher than Lf1-b;when the polysaccharide sample concentration is greater than1.5 mg/mL,the DPPH free radical scavenging ability of Lf1-b is higher than Lf1-a.In summary,through the optimization of liquid fermentation and fermentation conditions,a large number of edible fungus mycelium can be obtained in a short time and its yield can be increased.Tf526 Tremella extracellular polysaccharide has good antioxidant capacity. |
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