Optimization for betulin production from mycelial culture of Inonotus obliquus by orthogonal design and evaluation of its antioxidant activity

Abstract

This paper is concerned with optimization of submerged culture conditions for the mycelial growth and betulin production by Inonotus obliquus by one-factor-at-a-time and orthogonal experiment design. Among the variables of medium components, glucose, yeast extract, and MgSO4 were identified to be the most suitable carbon, nitrogen, and mineral sources, respectively. The optimal temperature and initial pH for mycelial growth and betulin production were found to be 25°C and 6.0, respectively. Subsequently, the concentration of glucose, yeast extract, and MgSO4 were optimized using the orthogonal experiment design. The optimal concentration for the enhanced production are determined as 30g/L glucose, 3g/L yeast extract, 5mmol/L MgSO4·7H2O for mycelial yield, and 30g/L glucose, 3.5g/L yeast extract, 5mmol/L MgSO4·7H2O for betulin production, respectively. The subsequent verification experiments confirmed the validity of the models. Under optimal culture conditions, the maximum betulin concentration in a 5-L stirred-tank bioreactor reached to 69.37mg/L. Furthermore, the morphological parameters of the pellets were characterized by their mean diameter, circularity, roughness and compactness. It was proved that mycelial growth and pellet morphology (i.e. compactness, mean diameter and roughness) may be the critical parameters affecting betulin production. In addition, betulin showed the potential antioxidant capacities on scavenging DPPH radical and hydroxyl radical.