Production optimization, preliminary characterization and bioactivity of exopolysaccharides from Incutis tamaricis (Pat.) Fiasson & Niemela

• The culture conditions for Incutis tamaricis were optimized by response surface methodology.
• The molecular features of EPSs were investigated by an SEC/MALLS system.
• Fr-II was exhibited higher antioxidant and antitumour activities than Fr-I.
• The molecular mass of the polysaccharides plays a main role in the enhancement of the bioactivity.

The aim of this work was to optimize the submerged culture medium for exopolysaccharides (EPS) production from Inocutis tamaricis (Pat.) Fiasson & Niemelä. The molecular characterization and the evaluation of antioxidant activity and antitumor activity in vitro of EPS were carried out as well. The one-factor-at-a-time method was adopted to investigate the optimal initial pH and temperature as 8.0 and 25 °C, respectively. The optimal culture condition was obtained as follows: sucrose 64.09 g/L and tryptone 5.24 g/L by central composite design (CCD). Under optimal culture condition, the maximum EPS concentration in shake flask was 5.89 g/L. Two groups of EPSs (designated as Fr-I and Fr-II) 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 and Fr-II of EPS were determined to be 8.948 × 104 and 6.421 × 104 g/mol, respectively. The SEC/MALLS analysis revealed that the molecular shapes of the Fr-I and Fr-II were the rigid sphere suspected to be the aggregates of complex polysaccharides. Furthermore, Fr-II was exhibited higher antioxidant and antitumour activities than Fr-I. Finally, FT-IR spectroscopy was used for obtaining vibrational spectra of the Fr-II EPS and the obvious absorption peaks at 916.5 and 884.0 cm−1 revealed the co-existence of α and β configuration. The carbohydrate composition analysis revealed Fr-II EPS was mainly composed of mannose, glucose and talose.