Optimization of Growth Conditions of Lentinus edodes Mycelium and Polysaccharides on Walnut Shell by-Products Using Response Surface Analysis

Lentinus edodes (L. edodes) is one of the most widely used traditional Chinese medicines and a high producer of various bioactive compounds such as polysaccharides. It has been shown that L. edodes polysaccharides (LEPLS) have several physiological effects with potential medical applications. In addition, the ability of L. edodes to grow and produce bioactive compounds on industrial by-products makes it an excellent candidate for the lage-scale production of such compounds. The objective of this study was to optimize mycelium and polysaccharide production by L. edodes on walnut shell through a two-step procedure including a one-factor-at-a-time approach to select the most important factors and a response surface methodology design to determine their optimum combinations. Several factors were evaluated in the first step and among them inoculum size, incubation time, and C/N ratio were selected for optimization of using RSM. The RSM model estimated that a maximal yield of biomass and LEPLS (0.043 mg/g and 46.80 mg/g respectively) could be obtained when inoculum size, incubation time, and C/N ratio were set at 23.41, 30, 10 units, respectively. These values were also verified by validation experiments.