The major nutrients, pH and temperature were evaluated for the exopolysaccharide (EPS) production by Daedalea dickinsii in submerged culture to derive an optimal medium composition and conditions as follows: 50 g/L maltose, 5 g/L soy peptone, 5 mM CaCl2, at pH 6.0 and 28 °C. A purified EPS fraction was attained from gel filtration chromatography and its major molecular characteristics were determined. FT-IR spectral analysis revealed the prominent characteristic groups of polyhydric alcohols. GC analysis and NMR spectrum showed its major molecular composition of glucose and galactose. Furthermore, thermogravimetric analysis indicated its degradation temperature (Td) of 189 °C. The antioxidant activity of the EPS fraction showed a correlation with the molecular properties. It might be attributed to the functional groups in the EPS fraction, which can donate electrons to reduce the radicals to a more stable form or react with the free radicals to terminate the radical chain reaction.

•A novel Trametes gibbosa was isolated and identified.•Culture conditions for EPS yield were optimized by RSM.•Molecular features of four EPS fractions were investigated by SEC/MALLS.•The hypolipidemic effects of T. gibbosa EPS were investigated in vivo.The submerged fermentation for extracellular polysaccharide (EPS) production from Trametes gibbosa was optimized. An optimal medium for EPS production was obtained through central composite design (CCD) as follows: 53.12 g/L maltose and 4.21 g/L polypeptone in distilled water. Furthermore, 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 mass of Fr-I was determined to be 3.872 x 105 g/mol and its molecular shape was revealed to be a rigid rod in an aqueous solution. Finally, the hypoglycemic effect of the EPS, investigated in streptozotocin induced diabetic mice, decreased plasma glucose, total cholesterol and triacylglycerol concentrations by 17.4%, 14.0% and 12.6%, respectively. The results indicate the potential of this EPS to prevent hyperglycemia in diabetic patients.

An optimal medium for exopolysaccharides (EPS) production was obtained through one-factor-at-a-time method and response surface methodology. Under optimal culture medium, the maximum EPS concentration in shake flask was 5.16 g/l. Two groups of EPSs (designated as Fr-I and Fr-II) were obtained from the culture filtrates by size exclusion chromatography/multiangle laser light scattering, and the weight average molar masses (Mw) of Fr-I and Fr-II were determined to be 4.098 × 104 and 1.114 × 104 g/mol, respectively. The molecular confirmation of Fr-I was revealed to be a rigid rod form in aqueous solution. Moreover, monosaccharide composition and characteristic groups were investigated by GC and Fourier transform infrared, respectively. Finally, pharmacology experiment in vitro indicated EPS Fr-II of Pleurotus eryngii exhibited higher antioxidant and antitumor abilities than Fr-I, which might be attributed to the different molecular weights and chemical compositions in the EPS fraction.

Optimization of culture conditions for exopolysaccharide (EPS) by Funalia trogii in submerged culture was investigated using one-factor-at-a-time method and uniform design (UD). Under the optimized conditions, the maximum concentration of EPS was 8.68 g/l. After EPS was deproteinized by Sevag method, two groups of EPSs (designated as Fr-I and Fr-II) were obtained from the culture filtrates by gel filtration chromatography on Sepharose CL-6B. Furthermore, EPSs were characterized by size exclusion chromatography (SEC) coupled with a multiangle laser-light scattering (MALLS) and refractive index (RI) detector system. The weight-average molar masses of the Fr-I and Fr-II were determined to be 1.007 × 105 and 2.393 × 104 g/mol, respectively. The root mean square (RMS) radii for both peaks ranged from 9.7 to 10.8 nm with no clear trends. Pharmacology experiments indicated F. trogii EPS were useful to the therapy of free radical injury and cancer diseases.Highlights► The culture conditions for EPS yield from Funalia trogii were optimized by uniform design. ► The molecular features of EPSs were investigated by a SEC/MALLS system. ► The antioxidant and antitumor activities of F. trogii EPS were investigated in vitro.

The aim of this work was to investigate the fermentation optimization, molecular characterization, and antioxidant activity in vitro of exopolysaccharides (EPS) from Morchella crassipes in submerged culture. Firstly, an optimal medium for EPS production was obtained by single-factor experiment and central composite design as follows: maltose 44.79 g/L and tryptone 4.21 g/L. Then, one fraction of EPS was obtained from the culture filtrates by size exclusion chromatography and the molecular characteristics were examined by a multi-angle laser light scattering and refractive index detector system. The weight-average molar mass and the polydispersity ratio of the EPS fraction were revealed to be 1.961 × 104 g/mol and 1.838, respectively. FT-IR spectroscopy was used for obtaining vibrational spectra of the purified EPS fraction. Finally, the antioxidant activity of EPS was investigated and the relationship with molecular properties was discussed as well.