Production and Chemical Characterization of Exopolysaccharides by Antarctic Yeasts <i>Vishniacozyma victoriae</i> and <i>Tremellomycetes</i> sp.
2022
Snezhana Rusinova-Videva | Manol Ognyanov | Yordan Georgiev | Margarita Kambourova | Aleksandar Adamov | Vasilena Krasteva
The study aimed to investigate exopolysaccharides (EPSs) produced by two Antarctic yeasts isolated from Livingston Island. The species were identified as <i>Vishniacozyma victoriae</i> (V) and <i>Tremellomycetes</i> sp. (T) based on a molecular genetic analysis of ITS1-5.8S-ITS4 regions of the 18S rRNA gene. The EPS production was investigated under stress conditions in culture flasks and a bioreactor. Different chromatographic (HPLC-RID, HPSEC-RID) and spectral (FT-IR) analyses were employed to characterize EPSs. <i>Tremellomycetes</i> sp. accumulated 7 g/L biomass and 4.5 g/L EPS after 120 h of cultivation. The total carbohydrate content of V-EPS and T-EPS was 75.4% and 79.0%, respectively. The EPSs mainly consisted of mannose (30–32%), which was followed by glucose, xylose, galactose, and small amounts of uronic acids (6.3–7.0%). EPSs had appreciable amounts of proteins (11–12%). The FT-IR spectra contained absorption bands typical for hetero-mannans and <i>β</i>-glucans (797–1033 cm<sup>−1</sup>). EPSs were heterogeneous with a broad molecular weight distribution range (47 × 10<sup>4</sup>–68 × 10<sup>4</sup> g/mol). In conclusion, both yeasts synthesized high-molecular-weight heteromannans, and <i>Tremellomycetes</i> sp. stood out as being a better producer than <i>V. victoriae</i>. The current study also formed a basis for a better assessment of the potential for practical application of EPSs and yeasts in biochemical engineering and biotechnology.
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