Abstract:
Natural products from microbial sources have been invaluable as a source of therapeutic agents since ancient times. An interest in microbial natural products for other potential biotechnological applications such as a natural fungicide, food colorant etc. continued. However, one of the bottle necks in bioprospecting is the detection and identification of these compounds from complex mixtures. With the emergence of metabolomics, several metabolite profiling tools have been developed to provide a more comprehensive and accurate identification, separation and quantification of metabolites. These approaches pave way for the discovery of new compounds, which could be nontoxic, biodegradable and eco-friendly thereby replacing the synthetic ones. In Villas-Bôas metabolomics laboratory, one strain of Epicoccum purpurascens was isolated. The fungus was found to produce pigmented exudates which showed antifungal activity against various phytopathogens. The compound was identified and patented as epicoccaene. The study of the biosynthetic pathway involved in the synthesis of the compound was also carried out. Later on, 13 more fungal strains were added to the culture collection in our laboratory. Out of these thirteen fungal strains added, two were obtained from overseas. These strains had to be researched for understanding their overall characteristics and their possible potential in biotechnological applications, keeping the one isolated in the lab as a comparative reference. For this purpose genotypes and phenotypes of the different E. purpurascens strains had to be analysed and compared. Therefore the main aim of this research work was phenotyping various Epicoccum purpurascens strains based on their antimicrobial activity, pigment production and metabolite profile. Metabolite profiling was carried out using direct infusion time-of-flight mass spectrometry. The fungal strain SVB-F1, isolated in our laboratory showed a broader range of antimicrobial activity compared to the other strains. The HPLC analysis of the fungal extracts revealed the peak of the pigmented compound responsible for the antimicrobial activity and it was observed that eleven fungal strains out of fourteen possessed this pigmented compound. The grouping of E. purpurascens strains based on their genotyping, metabolite profiling and antimicrobial activity showed no correlation among each other. The metabolite profiling of the fungal strains yielded more than 250 mass fragments. PCA projection showed the clustering of the strains based on their metabolite profiles. The masses of the metabolites contributing to the major difference among the fungal strains were obtained using loading plot. Also hierarchical cluster analysis was carried out to distinguish among the fungal strains based on their metabolite profiles.