title: Rheological behaviors of an exopolysaccharide from fermentation medium of a Cordyceps sinensis fungus (Cs-HK1).
abstract: The rheological behaviors of an exopolysaccharide (EPS) from a Cordyceps sinensis fungus fermentation were investigated. The intrinsic viscosity of 1986 ± 55 mL/g indicated an extended and rigid chain for EPS. Shear-thinning behavior was observed and became apparent with increasing concentration. According to cross model, two critical transition concentrations (c(*) and c(**)) from dilute solution to semidilute and then to concentrated domain were 0.45 and 6.14 mg/mL. Flow activation energy was calculated by Arrhenius equation and decreased with increasing concentration, indicating a lower sensitivity to temperature. From dynamic frequency sweep, EPS system was classified to three regions including dilution solution (1.25mg/mL), entanglement network (3.75 and 5.00 mg/mL) and weak gel (≥ 7.50 mg/mL). Notably, the increase in η(*) at high frequencies was attributed to a large flow resistance depended on the rigid chain of EPS. Based on Winter-Chambon criterion, EPS formed gel at 2.6 mg/mL (cgel) and showed typical weak gel from temperature ramp and repetitive strain sweep.
authors.affiliation: College of Food Science and Technology, and MOE Key Laboratory of Environment Correlative Dietology, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Fengyuan
authors.initials: F
authors.lastname: Sun
authors.affiliation: College of Food Science and Technology, and MOE Key Laboratory of Environment Correlative Dietology, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: whuhql@gmail.com.
authors.forename: Qilin
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Department of Applied Biology & Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
authors.forename: Jianyong
authors.initials: J
authors.lastname: Wu
mesh_terms: D032661:Cordyceps / Q000737:chemistry*; D005285:Fermentation; D011134:Polysaccharides / Q000737:chemistry*; D012212:Rheology
chemical_list: D011134:Polysaccharides
keywords: Cordyceps sinensis; Exopolysaccharide; Rheological behaviors