A mechanistic study of the enhancing effect of Tween 80 on the mycelial growth and exopolysaccharide production by Pleurotus tuber-regium

Several new observations related to the enhancement effect of Tween 80 on the mycelial growth and exopolysaccharide production by the submerged fermentation of Pleurotus tuber-regium were reported in the present study. Firstly, it was found that the addition of Tween 80 on the 5th day could significantly increase the glucose consumption rate at the later stage of the fermentation compared to the control. Secondly, addition of Tween 80 could maintain the intact structure of the mycelial pellets of P. tuber-regium with little signs of disintegration as observed under microscope and kept the pH value of the fermentation broth at an acidic level lower than that of the control. Thirdly, the oleic acid (C18:1) composition in the mycelial cell membrane was significantly increased from 2.6% (in the control) to 18.5% (with addition of Tween 80) coincided with a decrease in the concentration of Tween 80 in the culture medium. These new findings provide some important insight to the elucidation of the detailed mechanism by which Tween 80 is used as a stimulatory agent in the submerged fermentation of mushroom mycelium.