Metabolic profiling of Antarctic yeasts by proton nuclear magnetic resonance-based spectroscopy

The continent of Antarctica, as a combination of constantly low temperatures, strong winds, short summer season, and high solar radiation, is a highly extreme habitat suggesting appropriate conditions for growth of psychrophilic microorganisms. Five psychrophilic yeast strains were isolated from the samples taken from the region of the Bulgarian Base on Livingston Island, Antarctica: Cryptococcus laurentii AL(65), Sporobolomyces salmonicolor AL(36), Debaryomyces hansenii, Leucosporidium scotii and Rhodotorula glutinis, and their biomass yield and exopolysaccharides production were investigated. Best growth was observed for L. scotii and C. laurentii AL(65), with 7.5 and 6.0 g/L biomass, respectively, and highest exopolysaccharide yield was established for L. scotii. Metabolic profiling revealed phylogenetically based diversity in the identified metabolic profiles. The proton nuclear magnetic resonance (H-1 NMR) spectroscopy analyses of compounds extracted from the biomass of the strains revealed significant differences in the metabolites between individual yeast strains in our investigation including: among the amino acids alanine, valine, threonine, leucine and tyrosine; some organic acids such as gamma-aminobutyric acid, acetic acid, formic acid and others. Glucose was identified in all investigated strains. The highest diversity of compounds was observed in D. hansenii strain, division Ascomycota. The main compounds in the metabolic profile of Basidiomycota strains were sugars. The statistical analysis revealed significant differences in the studied metabolites among the yeast strains. This result suggests that, together with 16S rRNA gene and enzyme gene analyses, metabolite profiling could be also used as a marker for a phylogenetic distance in fungi evolution.