| The fungi Monascus has been used to produce drug and food additives for a long time. Various physiological active substances in Monascus culture have been found. One of them is that the Monascus polysaccharide has the functions of immunomodulator and detoxification to protect liver. In this dissertation, the culture medium and fermentation conditions for producing Monascus polysaccharides through liquid state fermentation were researched. Extraction, purification and antioxidative activity of Monascus polysaccharides through liquid state fermentation and solid state fermentation were investigated as well.Through screening Monascus M7, Monascus Mx1and Monascus N conserved by laboratory, the strain Monascus N with higher polysaccharide yield was selected after comparing the production yields by three Monascus strains. Optimization of the liquid state fermentation medium resulted the culture medium formulation as follows:sucrose45g/L, yeast extract powder4.5g/L, KH2PO4·3H2O3.5g/L, MgSO4·7H2O0.85g/L. In these conditions, optimized yield reached829.6mg/L, which was21.3%larger than original yield of684.2mg/L. By single factor experiment and orthogonal test, the fermentation conditions were optimized as:Seed culture age was30h, inoculation volume was7.5%, initial pH of fermentation medium was5.75, liquid medium volume was162.5mL in a1000mL conical flask, and the fermentation lasted for84h. The highest yield of Monascus polysaccharides could be up to999.8mg/L, which was46.1%larger than original yield of684.2mg/L.Tests ascertained extraction and purification process of Monascus polysaccharides as: polysaccharides solution pH was adjusted8-9. Sediment was abandoned after stewing for some time, and then papain was added into colatuie, reacting for3hours in45℃, heat preservation for20minutes in80"C to inactivate enzyme. After that, it was cooled rapidly with stewing, filtrated with abanding sediment. Fanally,1/5Sevag was added (n-butyl alcohol:chloroform=1:4) with severe stirring to clear metaprotein, repeateding operating (operating five times) till no sedimeng between organic solvent and water. Industral spirit as much as four times concentrated solution was added to precipitating sediment, which was white after drying with no pigment. After DEAE-cellulose chromatography purification with elution by0.2mol/L NaCl,0.4mol/L Nad,0.6mol/L NaCl successively, polysaccharides were eluted completely. Pure white polysaccharides were obtained from vacuum freeze drying with no pigment at all.Through preliminary research on Monascus producing polysaccharides by coarse cereals state fermention, mass ratio1:2of coarse cereals and water was determined. The yield of Monascus polysaccharides was enhanced prominently by replenishing water halfway.The largest yield reached76.0mg/g, which was as about seventy-six times as that of optimied liquid state fermentation, and the largest yield was acquired from Monascus fermenting maize with replenishing water halfway.The antioxidant capacity of the Monascus polysaccharide was evaluated by spectrophotometry on its ability of scavenging hydroxyl radical(OH), superoxide anion radical(O2-·), and1,1-diphenyl-2-picrylhydrazy radical(DPPH·), total reducing power and the antioxidant capability on oils as well. Results showed that the scavenging effects of Monascus polysaccharide on OH,·OH,O2-· and DPPH-.were significant. The polysaccharide also had a strong total reducing power and antioxidant capability on oils. The antioxidant capability of Monascus polysaccharide from solid fermentation was stronger than that from liquid fermentation. All these activities had obvious concentration-dependent. |
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