Quantitative and morphologic analysis on exopolysaccharide and biomass production from a truffle endophytic fungus Hypocreales sp. NCHU01

• This study is the first report concerning Hypocreales sp. NCHU01 producing EPS.
• Quantitative relation between mycelial biomass and EPS production was built.
• RSM was carried out to optimize culture conditions for EPS in Hypocreales sp.
• Optimal EPS yield was 1329.3 mg/L, a 3.34-fold increase to the original medium.
• The EPS molecular weight was increasing over the cultivation time.

In this study, exopolysaccharides (EPS) produced from Hypocreales sp. NCHU01 was carried out in the submerged cultivation. To find the optimal conditions, factors such as carbon and nitrogen source concentrations, pH, temperature, magnesium ion, and potassium ion levels were considered. The results showed that the optimal conditions were as follows: sucrose, yeast extract, magnesium sulfate and potassium dihydrogen phosphate were 10.6 g/L, 10.92 g/L, 1.0 g/L and 1.01 g/L, respectively. The optimization conditions were set at 25 °C with an initial pH 6.5. The maximum EPS production was about 1329 ± 23 mg/L, which was 3.34-fold to that of the original condition. The sucrose consumption rate was calculated to be 8.89 (g/L/day). Biomass production and EPS production rates were 3.92 and 0.18 (g/L/day), respectively. The yields for EPS and biomass were calculated to be 0.02 and 0.44 (g/g), respectively. The study displayed an increasing molecular weight distribution in the harvested EPS over a longer cultivation time. The quantitative relationship between mycelial biomass and EPS production was also built.