The Effect Of Different Lignocellulosic Biomass On The Hiosynthesis Of Active Polysaccharides By Inonotus Obliauus In Submerged Fermentation

Inonotus obliquus is one of the most efficient wood-degrading white-rot fungus thatbelongs to the family Hymenochaetaceae of Basidiomycetes and causes thesimultaneous decay of lignin, cellulose, and hemicellulose. In nature, this fungusnamed ‘Chaga’, which rarely forms a fruiting body but usually an irregular shape ofsclerotial conk, is well known as one of the most popular medicinal species due to itstherapeutic effects. Polysaccharides, one of the main active components of I. obliquus,were reported to exhibit many biological activities such as antioxidant, antitumor,immune-stimulating effects. Nevertheless, the natural fruitbody of Inonotus obliquusis scarce, the price is expensive and there is no mature artificial culture method, sobetter development and utilization of Inonotus obliquus is meaningful and has greatvalue.In this thesis, in order to enhance biological polysaccharide synthesis efficiency byInonotus obliquus under submerged fermentation, we evaluated the bioconversioneffectiveness and efficiency of the lignocellulose in peanut shell, wheat straw, ricestraw and sugarcane bagasse into active extra-(EPC) and intra-cellular (IPC)polysaccharides by I. obliquus. The results indicated all the lignocelluloses, especiallywheat straw enhanced the production and antioxidant activity of I. obliquuspolysaccharides. The dynamic changes of monosaccharide compositions in the culturebroth in the different lignocellulosic materials-containing media during fermentationwere investigated and the mechanism of lignocellulose converted into activepolysaccharide and the promotion of active polysaccharide was explored.The experimental results are as follows:1. Extra-(EPC) and intra-cellular (IPC) polysaccharides: By comparison with thecontrol medium, the maximum exopolysaccharide productions in the peanut shell, wheat straw, rice straw and sugarcane bagasse medium indicated1.37,1.34,1.25and1.22g/L after9,11,11and10days of fermentation, which accounted for asignificant enhancement (p<0.05) of95.7%,91.4%,78.6%and74.3%inexopolysaccharide production than the control, respectively. Compared with controlmedium, only wheat straw promoted the accumulation of intracellularpolysaccharide.2. Chemical composition of polysaccharides: Compared with polysaccharide contentand protein content, the polysaccharide extracts were composed of very low phenolcontent. Except the protein content of the exopolysaccharide from sugarcanebagasse showed a little decline after deproteinization treatment, the carbohydrate,protein content and phenol content showed a significant increase afterdeproteinization treatment. The polysaccharide content of the extracts fromdeproteinated exopolysaccharides and crude endopolysaccharides weresignificantly higher than that from the crude exopolysaccharides.3. Monosaccharide composition of polysaccharides: Crude exopolysaccharides werecomposed of mannose, glucose, and galactose and a small amount of rhamnose,arabinose and xylose; Crude endopolysaccharides were composed of mannose andglucose and a small quantity of rhamnose, arabinose, xylose and galactose, amongthem, the propotion of glucose accounted for more than59%.4. The dynamic changes of monosaccharide compositions in the culture broth:Glucose was identified as primary monosaccharide during the period offermentation, particularly in the initial stage when overwhelming majority ofmonosaccharides existed in the form of glucose. Along with the increase offermentation time, the proprotion of glucose descented, meanwhile the sum of theproportion of other monosaccharides ascented accordingly. After fermented for tendays, the proportions of rhamnose, arabinose, xylose, mannose and galactose frompeanut shell, wheat straw, rice and sugarcane bagasse-containing medium increasedsignificantly, whereas the proportions from control medium increased slightly.5. Antioxidant activity: The positive control mannitol and polysaccharides exhibited ahydroxyl radical scavenging activity in a dose-dependent manner (0.5–5.0mg/mL). The hydroxyl radical scavenging activity of polysaccharides from thelignocellulose media were significantly stronger than that from the control mediumin the same concentrations implying antioxidant activity by Inonotus obliquus wasenhanced by employing lignocellulose decomposition. Moderate DPPH radicalscavenging activity of the extracts was evident at the tested concentrations from0.5to3.0mg/mL in a dose-dependent manner except the deproteinatedexopolysaccharide from rice straw medium. It was indicated that IPC from thecontrol medium showed a higher DPPH radical scavenging activity than theendopolysaccharides from lignocellulose media at lower concentration from0.5to3mg/mL, the result was very different from the results of hydroxyl radical-scavenging activity.