灵芝在牛蒡固体培养基中发酵工艺优化及菌丝多糖的体外抗氧化活性

Production and in Vitro Antioxidant Activity of Mycelial Polysaccharide from Ganoderma lucidum Utilizing Burdock(Arctium lappa L.) Root under Optimized Solid-State Fermentation Conditions

为提升牛蒡废弃物的利用价值,以低品质牛蒡作为营养基质,精选优良灵芝菌种作为发酵菌株,研究牛蒡固体发酵灵芝产多糖工艺及其体外抗氧化活性。采用单因素试验和响应面优化法确定了装瓶量、粉碎程度、液固比等工艺条件;利用水提醇沉法提取牛蒡固体发酵灵芝菌丝中多糖,并用苯酚-硫酸法测定其总多糖含量;多糖经脱蛋白、透析和脱色后,经红外光谱分析多糖特征,高效液相色谱测定其单糖组成;体外实验检测多糖对1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-trinitrophenylhydrazine,DPPH)自由基、超氧阴离子自由基和羟自由基的清除能力。结果表明:最佳发酵条件为液固比0.4 mL/g、装瓶量0.2 g/mL、粉碎程度过6目筛,在此条件下实际获得的多糖含量为24.85 mg/g;红外光谱分析表明所获得的菌丝多糖具有糖类物质的特征吸收峰;高效液相色谱检测其单糖组成为甘露糖、核糖、鼠李糖、葡萄糖、半乳糖等,其中甘露糖含量最高,是葡萄糖的7.6倍;抗氧化性检测表明随着牛蒡固体发酵灵芝菌丝多糖质量浓度的增加,其对DPPH自由基、超氧阴离子自由基和羟自由基清除能力逐渐增强,且清除率均大于70%,说明多糖具有较好的体外抗氧化活性。

In order to achieve value-added utilization of burdock root waste, the solid-state fermentation of low-quality burdock root by a high-yield polysaccharide-producing strain of Ganoderma lucidum(Leyss. ex. Fr.) Karst was optimized for improved production of mycelial polysaccharide and the in vitro antioxidant activity of the polysaccharide was assessed.The fermentation conditions including amount of medium contained in culture fiasks, degree of pulverization and liquid-tosolid ratio were optimized by combined use of one-factor-at-a-time method and response surface methodology. The mycelial polysaccharide from G. lucidum was extracted by water extraction and ethanol precipitation and was quantified by the phenol-sulfuric acid method. After being deproteinized and decolorized by dialysis, the polysaccharide was characterized by infrared spectroscopy and was determined for its monosaccharide composition by high performance liquid chromatography(HPLC). Besides, the in vitro antioxidant activity was evaluated by 1,1-diphenyl-2-trinitrophenylhydrazine(DPPH),superoxide anion and hydroxyl radical scavenging assays. The results showed that the optimal fermentation conditions were as follows: liquid-to-solid ratio 0.4 mL/g, medium-to-culture fiask ratio 0.2 g/mL, and use of particles passing through a 6-mesh sieve. The polysaccharide content of the mycelia harvested under the optimized conditions was 24.85 mg/g.Fourier-transform infrared spectroscopy(FTIR) analysis showed that the product had the characteristic absorption peaks of polysaccharide. The monosaccharide composition analysis showed that the polysaccharide was composed of mannose,ribose, rhamnose, glucose and galactose, with mannose being the most abundant monosaccharide, which was 7.6 times as high as glucose. Each of the free radical was over 70% scavenged by the polysaccharide, and the effect increased with increasing its concentration. Hence, the polysaccharide had good antioxidant activity in vitro.