Urea Regulates The Synthesis Of Extracellular Saponins And Its Antioxidant Activity Of Paecilomyces Cicada

Cordyceps cicadae is a traditional medicinal and edible fungus.Paecilomyces cicadae is the asexual stage of C.cicadae.C.cicadae contain many nutrient and pharmaceutical ingredients including amino acids,inorganic salts,polysaccharides,saponins,cordycepin,et al.In view of the bottleneck of shortage of natural C.cicadae resources and the difficulty in cultivating C.cicadae,which limits the utilization of C.cicadae resources,as well as little research on the active components of C.cicadae,the dissertation uses submerged culture technology to culture P.cicada mycelia to meet the market demand of C.cicadae and studied the saponin of C.cicadae.The main research contents include:the synergistic actions between urea and other medium compositions and between urea and cultural conditions increase the synthesis of saponins of P.cicadae;the transcriptomics was used to study the mechanism by which urea regulates the synthesis of extracellular saponins by P.cicadae and the effect of urea on the antioxidant activity of extracellular saponins.?1?The optimum culture medium of P.cicadae with high yields of saponin was obtained by the single-factor analysis of carbon sources,nitrogen sources,inorganic salts,and nutritional factors and by the response surface design of the synergistic actions between urea and these components.The optimum medium components contained 3.7%bran,4.43%xylose,4.73%fructose,1.14%glycerin,0.13%urea,0.85%fish meal peptone,0.16%KH₂PO₄,0.16%ZnSO₄,0.0136%VB₂,0.0145%VC.?2?The optimum cultivation conditions to obtain the maximum extracellular saponin yield included culture temperature 26?,culture speed 160 rpm,inoculation volume 5%,media volume 105 mL,cultured time 108 h.Under the optimal culture conditions,the yield of saponin of P.cicadae was up to 14.73 mg/mL.?3?The transcriptomics was applied to analyze the mechanism for urea to regulate saponins synthesis by P.cicadae.The results showed that the 17,321 genes of P.cicadae was assembled by the short reads assembly software Trinity,and that urea resulted in 1,800 differential genes,in which 718 genes were upregulated and 1082genes were downregulated;After enrichment of GO function,the 1416 differential genes resulted from urea were annotated into GO function analysis;in specific genes KEGG pathway,630 differential genes caused by urea mainly concentrated in metabolism.The sterol regulatory element binding protein genes was found that control the synthase of saponin by P.cicadae.?4?The three systems including DPPH·scavenging rate,·OH generation inhibiting rate and Ferric reducing antioxidant power were used to study the difference in in vitro antioxidant capacity of two saponins synthetized by P.cicadae in the presence/absence of urea.The results showed that the two saponins have good antioxidant capacity,and its capacity is dose-dependent on saponin concentration.The saponin in the present of urea significantly enhanced the DPPH·scavenging rare,the·OH generation inhibition rate and the Ferric reducing antioxidant power.Kinetic analysis proved that the composition ratio of saponins was changed in the presence of urea.These components ratio of saponin increased who possess the stronger affinity to DPPH·,higher·OH generation inhibition rate and Ferric reducing antioxidant power.The inhibition of·OH generation by saponin is competitive type.