Improving The Diversity Of Secondary Metabolites From Microorganisms By Solid-state Fermentation Technique

Microorganisms are special in physical structure and unique natural environment. Most of them can produce a weide variety of secondary metabolites, which are the important resources of new skeleton compounds and the lead compounds in drug discovery. Exploring the potential of microorganisms to produce more new skeleton compounds is significant. After years of developing and using of the microorganisms, it became more and more difficult in discovering new drugs or lead compounds. To improve the diversity of secondary metabolites, the solid-state fermentation was studied by comparing the secondary metabolites from actinomycetes and fungi in solid-state fermentation and liquid-state fermentation.First, Banna Streptomyces DL1026which produces manumycin A and its derivatives was used as experimental subjects, to study the diversity difference of secondary metabolites between the solid-state fermentation condition and liquid-state fermentation condition, and the solid-state fermentation and extraction conditions were optimized. The factors which have influence on diversity of secondary metabolites, including the types of culture media, fermentation time and the optimum initial moisture were mainly studied. The culture medium containing of wheat bran with80%initial moisture, fermentation for11days were selected as the best fermentation conditions. The optimum extraction condition was given as follows: Both the fermentation culture and the blank control soaking in anhydrous alcohol (70%final volume)with the ultrasonic extraction, then the filtrate was obtained by pump filter and concentrated till to dryness undervacuum with rotary evaporator.the products were extracted with3mL of methanol, then passed through Sep-pak extraction column.eluated with20%ethanol firstly and the eluent was discarded, then eluated with80%ethanol and collected the solution samples,finally determined by HPLCSecondly, the comparison experiments for the kinds of secondary metabolites which34kinds of soil actinomycetes and45kinds of marine fungus produced in the optimum solid-state fermentation and liquid-state fermentation condition were performed. The results showed that no effective secondary metabolite peaks were detected in the5.9%and38.2%of actinomycetes fermented with solid and liquid state manner, respectively; More effective secondary metabolite peaks were found in85.3%of the strains with solid-state fermentation than that with liquid fermentation,8.8%of the strains showed the same number of effective secondary metabolite peaks:Totally, the number of effective secondary metabolite peaks from35kinds of actinomycetes detected under solid-state fermentation was3.5times higher than that under liquid-state fermentation:Deducting the repeated metabolites in different strains.34kinds of metabolites were detected from35kinds of actinomycetes under solid-state fermentation.which were2times higher than that under liquid state fermentation. abolite peaks.For marine fungi, no effective secondary metabolite peaks were detected in the8.9%and20%of actinomycetes fermented with solid and liquid state manner, respectively; More effective secondary metabolite peaks were found in46.7%of the strains with solid-state fermentation than that with liquid fermentation.13.3%of the strains showed the same number of effective secondary metabolite peaks;Totally, the number of effective secondary metabolite peaks from44kinds of marine fungi was24%higher in solid-state fermentation than in liquid-state fermentation. Deducting the repeated metabolites in different strains,40kinds of metabolites were detected from45kinds of marine-fungi under solid-state fermentation, which were48%higher than that under liquid state fermentation.Thirdly,strains with more effective secondary metabolites peaks in solid-state fermentation than in liquid-state fermentation were rescreened and optimized the fermentation conditions. Then,the research on chemical screening of secondary metabolites from strain DL45as well as the16SrDNA strain identification was performed. And at last.3fractions were obtained.This study shows that solid-state culture method can significantly improve the diversity of the microbial secondary metabolites as well as fully explore the potential to generate new secondary metabolites form the existing microbial resources.