Culture characterization of exopolysaccharides with antioxidant activity produced by Pycnoporus sanguineus in stirred-tank and airlift reactors

摘要

In the present study, exopolysaccharides (EPS) production and pellet morphology of Pycnoporus sanguineus was investigated in a 5-L stirred-tank (STR) and a 5-L airlift reactors (AR). Maximum EPS production (2.92 g/L) was obtained after 4 days of cultivation in STR, whereas, EPS concentration was maximal (2.14 g/L) after 2 days in AR. The morphological form of the fungal pellets in AR was more hairy than those in the STR. Furthermore, monosaccharide composition analysis indicated that purified EPS from STR was mainly composed of mannose and glucose, while purified EPS from AR mainly composed of glucose. Then, FT-IR spectral analysis of the purified EPS revealed prominent characteristic groups. Dye-inclusion studies with Congo red indicated that each EPS existed in a random coil conformational state. Furthermore, thermo gravimetric analysis (TGA) indicated the degradation temperature (Td) of the EPS from STR (152 °C) was higher than that of EPS from AR (116 °C). In addition, the antioxidant activities of the polysaccharides from different bioreactors were investigated. EPS from STR exhibited the higher antioxidant ability than EPS from AR, which might be attributed to the molecular weight, monosaccharide composition and the configuration of glycosidic bond in the EPS groups.