Enhancement of diosgenin production in Dioscorea zingiberensis cell cultures by oligosaccharides from its endophytic fungus Fusarium oxysporum Dzf17

Abstract

The effects of the oligosaccharides from the endophytic fungus Fusarium oxysporum Dzf17 as elicitors on diosgenin production in cell suspension cultures of its host Dioscorea zingiberensis were investigated. Three oligosaccharides, DP4, DP7 and DP10, were purified from the oligosaccharide fractions DP2-5, DP5-8 and DP8-12, respectively, which were prepared from the water-extracted mycelial polysaccharide of the endophytic fungus F. oxysporum Dzf17. When the cell cultures were treated with fraction DP5-8 at 20 mg/L on day 26 and harvested on day 32, the maximum diosgenin yield (2.187 mg/L) was achieved, which was 5.65-fold of control (0.387 mg/L). When oligosaccharides DP4, DP7 and DP10 were individually added to 26-day-old D. zingiberensis cell cultures at concentrations of 2, 4, 6, 8 and 10 mg/L in medium, DP7 at 6 mg/L was found to significantly enhance diosgenin production, with a yield of 3.202 mg/L, which was 8.27-fold of control. When the cell cultures were treated with DP7 twice on days 24 and 26, and harvested on day 30, both diosgenin content and yield were significantly increased and reached the maximums of 1.159 mg/g dw and 4.843 mg/L, both of which were higher than those of single elicitation, and were 9.19- and 12.38-fold of control, respectively.

Figure 1

Effects of oligosaccharide fractions DP2-5 (A), DP5-8 (B) and DP8-12 (C) on diosgenin yield of D. zingiberensis cell cultures. The error bars represent standard deviations (n = 3). Different letters indicate significant differences among the treatments at p = 0.05 level.

Figure 2

Effects of oligosaccharides DP4, DP7 and DP10 on dry weight (A), diosgenin content (B) and diosgenin yield (C) of D. zingiberensis cell cultures. The error bars represent standard deviations (n = 3). Different letters indicate significant differences among the treatments at p = 0.05 level.

Figure 3

Time courses of growth and diosgenin accumulation of D. zingiberensis cell cultures treated once with DP7 added on day 26 at 6 mg/L. The error bars represent standard deviations (n = 3).

Figure 4

Time courses of growth and diosgenin accumulation of D. zingiberensis cell cultures treated twice with DP7 added on days 24 and 26 at 6 mg/L. The error bars represent standard deviations (n = 3).