Effects of culture pH on the production of bioactive polysaccharides by Agaricus blazei in batch cultures

The effects of culture pH on the production, molecular weight distribution and the bioactivity of polysaccharides produced by Agaricus blazei were evaluated by four pH-controlled batch cultures. As the culture pH of each batch was controlled from 4.0 to 7.0, the maximum polysaccharide concentration increased from 561 to 1252 mg dm^-3, but the average molecular weight of the polysaccharides decreased monotonically from 1080 kDa to 600 kDa, the relative amount of β-glucan from 56% to 33%, and the TNF-α release by macrophage cells from 1440 to 760 pg per 5 × 10⁴ cells. Polysaccharides with higher molecular weights, β-glucan contents and bioactivities were obtained in the submerged cultures of Agaricus blazei at lower culture pH but with lower yields.