Antarctic microbial protein-rich extracts with cryoprotective potential for cell and viral preservation

Antarctic microorganisms are naturally adapted to extreme cold and freezing conditions, often through the production of cryoprotective biomacromolecules. In this study, 22 Antarctic bacterial and yeast isolates were initially characterized based on morphological traits and molecular identification. The isolates were subsequently screened for freezing resistance at -80 °C, and four representative strains (Rhodotorula sp. C01, Pedobacter sp. BGS4005, Psychrobacter sp. P61, and Salinibacterium sp. P45) were selected for protein extraction based on their survival rates. Intracellular and extracellular protein-rich extracts were then evaluated for cryoprotective activity in prokaryotic (Escherichia coli), eukaryotic (HEK293 cells), and viral (adenovirus) systems after 30-60 days of storage. Morphological and molecular characterization revealed 11 species displaying three main cellular morphotypes (cocci, coccobacilli, and bacilli), with variation in cell size. In E. coli, intracellular protein-rich extracts increased post-freezing viability, with the intracellular extract from Salinibacterium sp. P45, at 0.1 mg mL^-1, promoting an increase of approximately 3%. Extracellular protein-rich extracts from Pedobacter sp. BGS4005 and Psychrobacter sp. P61 further enhanced E. coli survival. In HEK293 cells, intracellular protein-rich extracts from Salinibacterium sp. P45 at 1 mg mL^-1 exhibited cryoprotective activity, maintaining cell viability above 20% following freezing. In addition, adenovirus suspensions treated with intracellular protein-rich extracts maintained viral titers over 60 days at 4 °C, with the extract from Psychrobacter sp. P61 at 1 mg mL^-1 showing no significant loss in viral titers. Together, these results highlight Antarctic microorganisms as a promising source of natural cryoprotective compounds and reinforce their relevance in extreme microbiology and cryopreservation biotechnology.