| Inonotus obliquus belongs to the white rot fungi, but also an extremely valuable medicinal fungi, which produce secondary metabolites of fermentation. There are many types, such as triterpenes, polyphenol, inulin, polysaccharides,with anti-oxidation, antitumor, antibacterial and other immune activities. It has a good therapeutic effect on diseases such as cardiovascular disease, gastritis, tuberculosis and cancer. However, the wild species of Inonotus obliquus is very rare, and because of the strict requirements on the growth environment and immature artificial technology, making the Inonotus obliquus can not meet the market demand. In this study, the liquid submerged fermentation technique was applied to the culture of Inonotus obliquus, which not only shortened the growth period, but also obtained a large number of active components of Inonotus obliquus.Because the growth of fungi is limited by the environmental conditions,such as oxygen, pH, temperature, etc. Through the optimization of the medium, the yield of polysaccharide can be improved. Our previous studies showed that the surfactant Tween 80, TritonX-100, by varying the mycelial permeability of the cell membrane,promoting the accumulation of polysaccharides. Our research group also found that pretreatment of Inonotus obliquus in liquid submerged fermentation can degrade lignocellulose and promote the production of polysaccharides.In this paper, we studied the promoting effect of surfactants on the degradation of lignocellulose and the synergetic action of the two on the active polysaccharides of Inonotus obliquus. The degradation rate of the three components of lignocellulose under the action of surfactants and the change of the surface structure of wheat straw after degrading were analyzed by scanning electron microscope (SEM). The results showed that Tween 80 could degrade lignocellulosic fibers. At the same time, the lignocellulosic degradation and the synergetic effects of surfactants Tween 80 and TritonX-100 on intracellular and extracellular polysaccharide production and antioxidant activity were clarified. The antioxidant activity and structure-activity relationship of extracellular and intracellular polysaccharides were also studied.The main results are as follows:1 . Through comparing mycelial biomass, polysaccharide content and DPPH scavenging activity of polysaccharide, the best mixed medium was obtained, which was Tween 80 + wheat straw and TritonX-100 + wheat straw. The Tween 80 and wheat straw mixed media could increase the yield and antioxidant activity of exopolysaccharides (EPS), and the promotion rates were 64.4% and 35.8%,respectively (p <0.05). TritonX-100 combined with wheat straw increased the yield of intracellular polysaccharides (IPS1, IPS2) and EPS by 23.2%, 13.5% and 79.7%,respectively (p <0.05).2. In order to study the interaction of surfactants and wheat straw,the polysaccharides from different sources were analyzed with the fermentation time.During the initial fermentation, the polysaccharide production increased rapidly, and it gradually became slow in the late fermentation. The polysaccharides from different mediums reached the maximum at the 9th day, which were 0.51mg/ml, 0.67mg/ml,0.79mg/ml and 0.85mg/ml, respectively. And the mixed medium of surfactant and wheat straw of the polysaccharide yield was higher than that of the single-wheat straw medium and the control medium. The possible reason is that the non-ionic surfactants Tween 80 and TritonX-100 changed the permeability of fungal cell membrane,promoted the absorption and utilization of nutrients in the fermentation broth, and also promoted the accumulation of extracellular polysaccharides.The IC50 values of DPPH radical scavenging polysaccharides in different medias are shown in the following table. The results showed that polysaccharides in mixed medium had the strongest antioxidant activity (the lowest IC50 value).Tablel. The IC50 values of polysaccharides from different medias (Control, Wheat Straw, WS+ Tween 80)Different letters in the same line represent significant differences (p <0.05)Different letters in the same line represent significant differences (p <0.05)3. The relationship between the polysaccharide composition and the antioxidant activity of polysaccharides was further studied by the chemical composition of polysaccharide (sugar, uronic acid, polyphenol, protein content) and monosaccharide composition. The polysaccharides in the mixed medium (wheat straw + Tween 80)had the highest content of polyphenol, uronic acid, sugar and protein, which the content was 2.84%, 7.75%, 43.28% and 20.53%, respectively. The results showed that the addition of wheat straw and Tween 80 promoted the chemical components of exopolysaccharide.4. The composition of monosaccharides was analyzed by gas chromatography(GC) on the extracellular polysaccharides from different sources of Inonotus obliquus.The results showed that the main components of polysaccharides were mannose,galactose and glucose, a small amount of rhamnose, arabinose, xylose. The results also showed that the highest rhamnose content of wheat straw + Tween 80-EPS was 6.5%, and that of wheat straw + Tween 80-EPS had higher glucose than that of control-EPS. Therefore, preliminary speculation that higher levels of rhamnose and glucose on the antioxidant activity of polysaccharides to promote the role of DPPH free radical scavenging activity results are more consistent.5. In order to understand the effect of Tween 80 on the yield and antioxidant activity of polysaccharides of Inonotus obliquus, the effect of Tween 80 on the degradation of lignocellulose by liquid fermentation of Inonotus obliquus was studied.After degradation, the degradation rates of cellulose, lignin and hemicellulose were 70.20%, 75.57% and 76.67%, respectively. And the degradation rate of cellulose,lignin and hemicellulose were significantly improved, which indicated that Tween 80 Table2. The IC50 values of polysaccharides from different medias (Control, Wheat Straw, WS + Triton X-100)promoted the degradation of wheat straw by Inonotus obliquus. Therefore, in the early stage of our group,the effects of surfactants and lignocellulosic degradation on the polysaccharide production of Inonotus obliquus were clarified separately,and the possible mechanism of the interaction was further clarified.In conclusion,the combination of surfactants and wheat straw could significantly promote the activity and yield of polysaccharide of Inonotus obliquus,and the addition of Tween 80 also promoted the degradation of wheat straw by Inonotus obliquus.The mechanism needs further study. Therefore, this paper has some significance for the fermentation of active fungal polysaccharides and the degradation of lignocelluloses by Inonotus obliquus. |
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