Kim Sang Woo, Xu Chun Ping, Hwang Hye Jin, Choi Jang Won, Kim Chan Woo, Yun Jong Won
Department of Biotechnology, Department of Natural Resources, and Center for Laboratory Facilities, Daegu University, Kyungsan, Kyungbuk 712-714, Korea.
Biotechnol Prog. 2003 Mar-Apr;19(2):428-35. doi: 10.1021/bp025644k.
Optimization of the submerged culture conditions for the mycelial growth and production of exopolysaccharide (EPS) from a newly isolated Cordyceps species (C. militaris NG3) was studied in flask cultures. The optimal temperature and initial pH for EPS production were 30 degrees C and 8.0, respectively. Sucrose (30 g/L) and corn steep powder (10 g/L) were the most suitable carbon and nitrogen source for both mycelial growth and EPS production. There was a distinguishable morphological changes in mycelium grown between organic and inorganic nitrogen sources. A smooth pellet growth with heavy hyphal thickness was observed in the medium containing organic nitrogen sources, whereas irregular pellets with less hairy region were formed in the medium containing inorganic nitrogen sources. More highly branched cells appearing in the medium of organic nitrogen sources seemed a favorable morphological form for both EPS production and mycelial growth. Under optimal culture conditions, the maximum concentrations of mycelial growth and EPS were 17.6 and 3.4 g/L in a 5-L stirred-tank fermenter. Four groups of EPSs (designated as Fr-I, Fr-II, Fr-III, and Fr-IV) were obtained from the culture filtrates by size exclusion chromatography (SEC), and their molecular characteristics were examined by a multiangle laser-light scattering (MALLS) and refractive index (RI) detector system. The weight-average molar masses of the Fr-I, Fr-II, Fr-III, and Fr-IV of EPS were determined to be 2.262 x 10(6), 3.348 x 10(5), 1.049 x 10(5), and 5.059 x 10(4) g/mol, respectively. All four EPSs showed very low polydispersity indices ranging from 1.00 to 1.18. The SEC/MALLS analysis revealed that the molecular shape of the Fr-I was a rigid sphere suspected to be an aggregate of complex polysaccharides, the Fr-II and Fr-III were nearly globular in shape, and the Fr-IV was an almost rodlike structure.
在摇瓶培养中研究了新分离的蛹虫草菌种（蛹虫草NG3）菌丝体生长和胞外多糖（EPS）产生的深层培养条件优化。EPS产生的最适温度和初始pH分别为30℃和8.0。蔗糖（30 g/L）和玉米浆干粉（10 g/L）是菌丝体生长和EPS产生最合适的碳源和氮源。在有机氮源和无机氮源上生长的菌丝体存在明显的形态变化。在含有有机氮源的培养基中观察到菌丝体呈光滑的颗粒状生长，菌丝较厚，而在含有无机氮源的培养基中形成的颗粒不规则，毛状区域较少。在有机氮源培养基中出现的高度分支细胞似乎是EPS产生和菌丝体生长的有利形态。在最佳培养条件下，5-L搅拌罐发酵罐中菌丝体生长和EPS的最大浓度分别为17.6 g/L和3.4 g/L。通过尺寸排阻色谱（SEC）从培养滤液中获得了四组EPS（分别命名为Fr-I、Fr-II、Fr-III和Fr-IV），并通过多角度激光光散射（MALLS）和折射率（RI）检测系统对其分子特性进行了检测。EPS的Fr-I、Fr-II、Fr-III和Fr-IV的重均摩尔质量分别测定为2.262×10⁶、3.348×1⁰⁵、1.049×1⁰⁵和5.059×1⁰⁴ g/mol。所有四种EPS的多分散指数都非常低，范围在1.00至1.18之间。SEC/MALLS分析表明，Fr-I的分子形状为刚性球体，疑似复杂多糖的聚集体，Fr-II和Fr-III的形状接近球形,Fr-IV为几乎呈棒状的结构。
