Enhancement of Diepoxin zeta Production by Yeast Extract and Its Fractions in Liquid Culture of Berkleasmium-Like Endophytic Fungus Dzf12 from Dioscorea zingiberensis

This study was to examine the effects of yeast extract (YE) and its fractions (YE1 and YE2) on the growth and diepoxin zeta(a spirobisnaphthalene with a diversity of bioactivities) production in liquid culture of Berkleasmium-like endophytic fungus Dzf12 from Dioscorea zingiberensis. When YE was applied to the liquid medium at 10 g/L on day 3 of culture, the diepoxin zeta production was most effectively enhanced 3.2-fold (378.70 mg/L versus 120.09 mg/L in control) after another 10 days culture. Feeding with 15 g/L of YE on day 9, the mycelia biomass reached 16.44 g/L, about 2.3-fold in comparison with the control (7.15 g/L). The polysaccharide fraction (YE1) was mainly responsible for stimulating diepoxin zeta accumulation, and the non-polysaccharide fraction (YE2) was mainly responsible for promoting mycelia growth. The results showed that the diepoxin zeta production in liquid culture of endophyte Dzf12 could be effectively enhanced by YE and its fractions.