Exopolysaccharide (EPS) Production by Endophytic and Basidiomycete Fungi

The screening of exopolysaccharides (EPS) produced by 52 isolates of endophytic and basidiomycete fungi was studied on two different media, PDB and PYGM. There were five isolates that could produce dried exopolysaccharide of more than 4 g/L (S. commune LF01962, LF01001, LF01581, Pycnoporus sp. MMCR00271.1, Pestalotiopsis sp. PP0005). The molecular weights of these exopolymers were found to be in the range of 2.5–500 kDa. These five exopolysaccharides, produced by five different fungal isolates, showed non-cytotoxic activity against NCTC clone 929 and HDFn cell lines. The selected fungal isolate of S. commune LF01962 was used for further optimization of different medium compositions affecting exopolysaccharide production using statistical methods. Among four conditions tested in the first step (xylose + peptone, glucose + (NH4)2HPO4, fructose + peptone, and mannose + yeast extract), mannose + yeast extract resulted in the highest exopolysaccharide production of 5.10 ± 2.00 g/L. In the second step using Plackett–Burman design, the optimal medium for S. commune exopolysaccharide production was found to consist of 40 g/L glucose, 5 g/L mannose, 20 g/L (NH4)2HPO4, 5 g/L yeast extract, 3 g/L monosodium glutamate, 0.5 g/L KH2PO4, 0.5 g/L K2HPO4, 0.2 g/L MgSO4, 1 mL/L trace elements, and 3 mL/L vitamin solution, which resulted in 8.16 g/L exopolysaccharide production. Exopolysaccharide production in a 5 L bioreactor using small pellets as seed inoculum was found to produce 18.28 g/L exopolysaccharide.