Optimizing of the Medium Composition for Mycelial Growth of Selenium-enriched Inonotus hispidus by Response Surface Methodology

In this study, the tolerance level of I. hispidus to inorganic Se was investigated. And the culture mediumfor mycelial growth of Se-enriched I. hispidus was optimized using response surface method (RSM). To determine the optimal components of the Se-rich medium, the effect of single factor to mycelial growth of I. hispidus (average mycelium growth rate was calculated as measurement index) was initially identified respectively. Box-Behnken design was then used to create a model for optimizing the Se-rich medium components. Meanwhile, Se content in the mycelia of Se-enriched I. hispidus was detected by ICP-MS. The results showed that the mycelial growth of I. hispidus was greatly influenced by the concentration of exogenous Se. The growth rate of I. hispidus began to be inhibited significantly at 37.25 mg/L Se concentration (P<0.05). And the maximal tolerant concentration of I. hispidus to Se was approximately at 298~596 mg/L. The suitable Se concentration, principal component and supplementary carbon source were selected and adjusted by the model, which predicted the significant effect could be obtained when the Se-rich medium contained bran, glucose, Se, MgSO₄, KH₂PO₄, V_B1 and agar at 56.8, 49, 2.24×10^-2, 0.75, 1, 1×10^-3 and 15 g/L, respectively. Verification of this recipe resulted in the average mycelium growth rate at 8.41 mm/d, which was 0.965 times higher than that cultivated by using the modified PDA medium with equivalent Se addition. And Se content in the mycelia of Se-enriched I. hispidus reached 31.584 μg/g. In this study, the optimal recipe of medium for mycelial growth of Se-enriched I. hispidus was obtained, which provided a basic information for producing mycelia and fruiting bodies of selenized I. hispidus or other subsequent studies.