Modeling and Optimum Extraction of Multiple Bioactive Exopolysaccharide from an Endophytic Fungus of Crocus sativus L

BACKGROUND: Crocus sativus L. (saffron) is a scarce plant that has been used as food flavoring agent, coloring agent, and traditional herbal medicine. METHODS: The bioactivity of exopolysaccharide (EPS) extracted from an endophytic fungus of C. sativus was examined for the first time by antioxidative, antitumor, and antibacterial assays. The extraction conditions for EPS were optimized by combining the response surface methodology with Box-Behnken design. RESULTS: EPS exhibited excellent scavenging activities against 1,1-diphenyl-2-picrylhydrazyl, hydroxyl and superoxide anion radicals, and moderate cytotoxicities against K562, A549, HL-60, and HeLa cells. The optimum extraction conditions for EPS were as follows: precipitation time of 16 h, precipitation temperature of 3.7°C, pH 7.2, and ratio of ethanol to fermented broth of 5:1 (L/L). Under the optimized conditions, the yield of EPS reached 162 ± 6 μg/L which was close to the predicted one (165 μg/L). Moreover, high-performance liquid chromatography of monosaccharide composition showed that EPS comprised mannose, glucose, galactose xylose, and arabinose in a molar ratio of 25.6:16.5:1.0:3.8:5.4. CONCLUSION: EPS may be an eligible substitute for C. sativus and a potential bioactive source applicable to pharmaceutical and food industries. SUMMARY: Exopolysaccharide (EPS) from endophytic fungus of Crocus sativus was studied for the first time. EPS extraction was optimized by combining response surface methodology with Box-Behnken design. Monosaccharide composition and EPS structure were identified by high-performance liquid chromatography and Fourier-transform infrared spectroscopy. Abbreviations used: EPS: Exopolysaccharide, RSM: Response surface methodology, BBD: Box-Behnken design, DPPH: 1,1-diphenyl-2-picrylhydrazyl, V(C): Ascorbic acid, MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, LB: Luria Bertani, DMSO: dimethyl sulfoxide, PMP: 1-phenyl-3-methyl-5-pyrazolone, FT-IR: Fourier transform-infrared, HPLC: High-performance liquid chromatography, 3D: Three-dimensional, 2D: Two-Dimensional.