Bistage Control Technique for Improving Ergosterol and Polysaccharides Production from Agaricus blazei Murrill by Submerged Fermentation

On the basis of previous studies, the fermentation production of ergosterol and polysaccharides from Agaricus blazei Murrill was further optimized in a 5L mechanically stirred-fermenter. The bi-stage control technique, that is, shifting the pH and culture temperature from 4.43 and 26 degrees C to 5.43 and 22 degrees C respectively at 48 hr, was introduced to improve mycelia growth and exopolysaccharide production. The other parameters were set at 309 rev/min of agitation speed, 1 vvm (3.0 L/min) of aeration rate, 8%of inoculation density and 0.015 Mpa of tank pressure. The yield under the optimal condition were 11.52 g/L of dry mycelia, 107 mg/L of ergosterol, 260 mg/L intracellular polysaccharide and 298 mg/L exopolysaccharide, which were 7.9%, 44.6%, 21.5% and 3.7% higher than the pH-uncontrolled fermentation at constant temperature, respectively.