Screening of Irpex lacteus mutant strains and optimizing fermentation conditions

In the present study, mutant Irpex lacteus ILN10 was obtained via chemical mutagenesis combined with a series of screening process. Results from internal transcribed spacers identification and random amplified polymorphic DNA confirmed that ILN10 is a new high-yield producing Irpex lacteus, which has already been preserved in China Center for Type Culture Collection. Compared with wild strain, the mycelium yield and active ingredients content (intracellular adenosine, mannitol and polysaccharide) of ILN10 were enhanced significantly. Furthermore, various chemometrics methods were applied to optimize the fermentation medium of Irpex lacteus ILN10 progressively. Three parameters (lactose, yeast extract powder and (NH 4 ) 2 SO 4 ) selected via Plackett-Burman design were further optimized by response surface methodology. Optimum fermentation medium consisted of (g/L): lactose 26.45, yeast extract powder 24.09, (NH 4 ) 2 SO 4 0.23, KH 2 PO 4 0.5, MgSO 4 •7H 2 O 0.5, and VB 1 0.15. The average optimum D value was 0.5225, 1.99-fold as high as that obtained from the original medium.