Optimization and Scale-up of Extracellular b-glucan Production by Ophiocordyceps dipterigena BCC 2073 in Low-Cost Media

The optimization of β-glucan production by Ophiocordyceps dipterigena BCC 2073 was carried out. For the three-step optimization performed in 250-mL Erlenmeyer flasks, at the first step, the maximum β-glucan production of 16.48±0.60 g/L was obtained using molasses and malt extract. During the second step, we sought to find an alternative carbon source; the highest β-glucan production of 16.96±1.33 g/L was obtained using yeast extract and hydrolyzed cassava starch. The third step involved the optimization of nitrogen sources, and the highest β-glucan content (18.16±0.15 g/L) was obtained with yeast extract. To reduce the use of yeast extract for β-glucan production, a fractional factorial design at 2 levels was applied after the three-step optimization to reduce the concentration of yeast extract by combination with other suitable inorganic nitrogen sources. The medium consisting of 2.5 g/L yeast extract as a sole nitrogen source yielded 24.65±2.21 g/L β-glucan production. At the last step of optimization, the highest βglucan production of 35.77±3.01 g/L was obtained in the medium consisting of 68.8 g/L hydrolyzed cassava starch, 2.62 g/L molasses and 2.5 g/L yeast extract using central composite design. The evaluation of b-glucan production was carried out in a 5-L bioreactor, and 76.87±0.96 g/L of material was obtained.