Bacterioruberin extracts from a genetically modified hyperpigmented Haloferax volcanii strain: Antioxidant activity and bioactive properties on sperm cells.

AIMS: To examine the antioxidant activity of Bacterioruberin (Bctr)-rich extracts isolated from a hyperpigmented-genetically modified Haloferax volcanii strain (HVLON3) and to investigate the effect on cold-sensitive ram sperm cells.

METHODS AND RESULTS: The strain HVLON3 produces higher Bctr amounts than most haloarchaea (220 ± 13 mg/g DW). HVLON3-Bctr extract has higher antioxidant activity than β-carotene (3-fold) as evaluated using 2,2 diphenyl-1-picrylhydrazyl combined with Electron Paramagnetic Resonance analysis (EC50 4.5 x 10-5 mol l-1 vs. 13.9 x 10-5 mol l-1 , respectively). Different concentrations of HVLON3-Bctr extracts were assayed on ram sperm after freezing/thawing and physiologically relevant parameters were examined. Extracts containing 7 and 20 μmol l-1 Bctr significantly improved cell viability (p<0.0001), total and progressive motility (p<0.0001) and sperm velocities (p=0.0172 for curvilinear velocity VCL, p=0.0268 for average path velocity VAP and p=0.0181 for straight-line velocity VSL) and did not affect other parameters evaluated.

CONCLUSIONS: HVLON3 is an excellent source of natural microbial C50 carotenoids with applicability in Biotechnology, Biomedical and Veterinary fields. HVLON3 Bctr-extract improves the quality of cryopreserved ram sperm cells and could be applied to increase insemination yields.

SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides insight on the bioactive properties of a bioproduct derived from haloarchaea (carotenoids) which are so far underexploited. This article is protected by copyright. All rights reserved.