Optimization of the fermentation process of Cordyceps sobolifera Se-CEPS and its anti-tumor activity in vivo

BACKGROUND: Cordyceps sobolifera (C. sobolifera) isolated from cicadae was used as the starting fungus to produce selenium-enriched C. sobolifera extracellular polysaccharide (Se-CEPS). An orthogonal experimental design based on a single-factor experiment was used to optimize the C. sobolifera fermentation conditions, including the potato juice, peptone, and KH(2)PO(4) concentrations. Ultraviolet (UV) and infrared (IR) analyses of CEPS and Se-CEPS were conducted, as well as an in vivo anti-tumor analysis. RESULTS: Under optimal conditions (i.e., 40 potato juice, 0.4 KH(2)PO(4), and 0.5 % peptone), the fermentation yield of Se-CEPS was 5.64 g/L. UV and IR spectra showed that Se-CEPS contained a characteristic absorption peak of a selenite Se = O double bond, demonstrating the successful preparation of Se-CEPS. Activity tests showed that Se-CEPS improved the immune organ index, serum cytokine content, and CD8(+) and CD4(+) T lymphocyte ratio in colon cancer CT26 tumor-bearing mice, thereby inhibiting tumor growth. When combined with 5-FU, Se-CEPS reduced the toxicity and enhanced the function of 5-FU. CONCLUSION: The result of these experiments indicated that orthogonal experimental design is a promising method for the optimization of Se-CEPS production, and the Se-CEPS from C. sobolifera can improve the anti-tumor capacity of mice. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13036-016-0029-0) contains supplementary material, which is available to authorized users.