Study On Optimization Of Fermentation Conditions Of Xyloketal B By A Marine-derived Fungus Xylaria Sp.2508#

Xyloketal B, a novel compound, has been isolated from cultures of a marine-derived macrofungus Xylaria sp.2508#. Its chemical structure had novel features which were first discovered. The pharmacological experiment stated that xyloketal B exhibited excellent protection against several cell injuries and was considered as a promising cardiovascular drug candidate. This study focused on the key medium component that could make Xylaria sp. 2508# produce xyloketal B and a set of methods that were used to extract and analyse the product. In addition, the production of xyloketal B was enhanced by a better inoculum method and the preliminary study on the medium components.In order to elucidate species relationship of Xylaria sp.2508#, it was identified by molecular biology. Additionally, the key component in medium where Xylaria sp.2508# could produce xyloketal B is malt extract by screening various carbon sources and nitrogen sources. Moreover, The inoculum method in fermentation of xyloketal B by Xylaria sp.2508# was regulated, the inoculum become more uniform and the pellets in fermentation was smaller by agar addition in seed culture. The results showed that the optimal inoculum method reduced the period of fermentation and enhanced the xyloketal B production which was increased by about 290%, rising from 4.5 mg/L to 12.4 mg/L.Meanwhile, the culture medium conditions were investigated, mainly the effect of metal ions on biomass and production of xyloketal B. CuSO4, MgSO4, CaCl2 had a positive effect on production, while ZnSO4, MnCl2, KH2PO4 inhibit the synthesis of xyloketal B. Besides, the biomass was greatest when pH value was 4, while the production of xyloketal B was achieved highest when pH value was 7. In the process of MgSO4 addition, the production of xyloketal B enhanced from 16.6 mg/L to 24.7 mg/L, increasing by about 33%. Additionally, there was a positive effect on xyloketal B production within a certain range of shearing force, while the results of oxygen carrier addition indicated that it was not necessary to keep high dissolved oxygen concentration during the fermentation of Xylaria sp.2508#.