Kinetic Modeling of Growth and Mycelial Exopolysaccharide Production by Lentinus edodes (Shiitake Edible Mushroom)

Background and Objective: Lentinus edodes (Shiitake) is a rich source of secondary metabolites, including exopolysaccharides. These compounds strengthen the immune system and play essential roles in prevention and treatment of several diseases, including cancers. A way to increase production of polysaccharides is the use of elicitors. Examples of these elicitors include microbial volatile organic compounds, which are produced in microo-rganism co-cultures. The objective of this study was to investigate effects of these compounds on production of Shiitake exopolysaccharides. Material and Methods: To decrease cultivation time, Shiitake was cultured in four culture media, including (1) potato dextrose broth, (2) potato dextrose broth and D-glucose, (3) malt extract broth and (4) malt extract broth and D-glucose. After selecting appropriate culture media, fungal growth curve, kinetic growth of pellets and filamentous morphology were studied. Novel method of simultaneous aerial co-culture was used to increase production of Shiitake exopolysaccharides, which acted as an elicitor by inducing microbial volatile organic compounds of other microorganisms. Microbial volatile organic compounds were analyzed using gas chromatography-mass spectroscopy. Results and Conclusion: Malt extract medium containing glucose was selected for submerged and solid cultures of Shiitake and the growth time decreased to 18 d. Shiitake biomass production included 11 g.l-1 . Filamentous morphology included higher production rates due to higher surface-to-volume ratios, compared to that the pellet morphology did. Shiitake fungal biomass and exopolysaccharides in co-cultures with Aspergillus niger included 14 and 4 g.l-1 , respectively. Furthermore, biomass and exopolysaccharides included 11 and 4.7 g.l-1 in co-cultures with Schizophyllum commune, respectively. Microbial volatile organic compounds produced by Aspergillus niger and Schizophyllum commune in cocultures, as elicitors, increased biomass and exopolysaccharide productions in Shiitake. Therefore, it suggests that microorganism co-cultivation is a low-cost effective method for Shiitake exopolysaccharide production.