Optimization of submerged culture conditions for mycelial growth and exopolysaccharides production by Agaricus blazei

Abstract

The influences of inoculum size, pH, and medium composition on mycelial growth and exopolysaccharides (EPS) production were investigated in shake flasks and in a bioreactor. The optimum inoculum size for both mycelial growth and EPS production was identified to be 10% (v/v) in shake flask cultures. The optimal initial pH for mycelial growth and EPS production in shake flask cultures were found to be 5.0 and 7.0, respectively. However, the optimal pH was 5.0 for both mycelial growth and EPS production in bioreactor cultures where the pH was regulated. The optimal mass ratio of the two major carbon sources, glucose to dextrin, was 1:4. The optimal mass ratio of the two major nitrogen sources, yeast extract to soytone peptone, was 2:1. When 500 mg 1 -1 of MnSO 4 .5H 2 O was added to the bioreactor culture, both mycelial growth and EPS production were enhanced by approximately 10%. Under the optimized conditions, a mycelial biomass of 9.85 g 1 -1 and an EPS concentration of 4.92 g l -1 were obtained in 4 days.