Optimal conditions for mycelia biomass and extracellular polysaccharides of Grifola frondosa: Effect of agitation speed, inoculum ratio and initial pH

Abstract

Grifola frondosa, a medicinal and edible mushroom, has shown different bioactive compounds, such as polysaccharides with anticancer and other therapeutic properties. In the present research, the mycelia of G. frondosa were cultivated in shaking flasks to investigate the effects of agitation speeds, inoculum ratios, and initial pH on pellet morphology, biomass, and extracellular polysaccharide (EPS) production. Furthermore, mathematical models for optimizing the three factors for biomass and EPS production were developed. The results show that the culture parameters including agitation speed, inoculum ratio, and initial pH influenced pellet morphology, biomass, and EPS production. The optimal conditions for biomass and EPS production were agitation speed at 105 and 111 rpm, inoculum ratio 3.1 and 3.3%, and initial pH 5.5 and 5.6, respectively. Under these conditions, the predicted maximum biomass and EPS were 5.28 and 2.35 mg/ml, respectively. The findings may be useful for future development of fermentation techniques for the production ofG. frondosa products. Key words: Grifola frondosa, biomass, extracellular polysaccharides, optimization.