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

Abstract

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−1 DW). HVLON3‐Bctr extract has higher antioxidant activity than β‐carotene (threefold) as evaluated using 2,2 diphenyl‐1‐picrylhydrazyl combined with Electron Paramagnetic Resonance analysis (EC50 4·5 × 10−5 mol l−1 vs 13·9 × 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 an insight on the bioactive properties of a bioproduct derived from haloarchaea (carotenoids) which are so far underexploited.

Haloterrigena sp. Strain SGH1, a Bacterioruberin-Rich, Perchlorate-Tolerant Halophilic Archaeon Isolated From Halite Microbial Communities, Atacama Desert, Chile

“…Also, cytotoxicity to HepG2 was demonstrated in cell extracts from a Halobacterium halobium and extracts from H. salinarium and Haloferax volcanii strains isolated at a solar saltern in Tunisia and brines in India (Abbes et al, 2013;Sikkandar et al, 2013). In fact, methanol extract of a genetically modified hyperpigmented Haloferax volcanii strain, rich in BR, showed beneficial effects on cryopreserved ram sperm, improving viability and motility after thawing (Zalazar et al, 2019). Our work has demonstrated that purified isomers and derivatives of BR from Haloterrigena sp.…”

“…Comparatively, a lower carotenoid content has been registered for other halophilic archaea; e.g., 45 µg g −1 of dry biomass in Halococcus morrhuae (Mandelli et al, 2012), 75 µg g −1 of dry biomass in H. turkmenica (Squillaci et al, 2017) and 335 µg g −1 of dry biomass Haloarcula japonica (Yatsunami et al, 2014). Recently, Zalazar et al (2019) have reported that the bacterioruberin content (220 mg g −1 dry weight) in a hyperpigmented, genetically modified Haloferax volcanii strain HVLON3 is higher than in other haloarchaea. The red-pigmented strain SGH1 accumulates BR when growing at high salinity (25% NaCl) but the BR content decreased nearly 20-fold after the SGH1 cells are transferred and adapted to grow at low salinity (15% NaCl).…”

Antioxidant, Antimicrobial, and Bioactive Potential of Two New Haloarchaeal Strains Isolated from Odiel Salterns (Southwest Spain)

“…Carotenoids from haloarchaea have shown anticancer and antihemolytic activities [ 12 ], and the ability to increase sperm cells viability after cryopreservation [ 13 ]. Furthermore, many natural carotenoids are used as food preservatives and pharmaceutical and cosmetic compounds due to their antioxidant and pro-vitamin properties [ 14 ].…”

Haloferax volcanii for biotechnology applications: challenges, current state and perspectives

“…H. volcanii predominantly produces the C 50 carotenoid bacterioruberin (82%) and its derivatives such as monoanhydrobacterioruberin (7%), b i s a n h y d r o b a c t e r i o r u b e r i n ( 2 % ) a n d dihydromonoanhydrobacterioruberin (2%), along with small amount of lycopene (0.3%) (Rønnekleiv 1995). A recent study has shown that bacterioruberin produced by H. volcanii is three times more effective as an antioxidant compared with β-carotene and improves the cell viability, motility and velocities of ram sperm cells (Zalazar et al 2019). HvLON3 strain, a conditional H. volcanii mutant for Lon protease produces 10-15 times more bacterioruberin than the parental strain given that Lon protease degrades the phytoene synthase, the rate limiting enzyme in carotenoid biosynthesis (Cerletti et al 2018).…”

“…Compared with other halophilic archaea, H. volcanii is better suited for heterologous pathway engineering due to its faster growth, readily available genetic toolkit and stable genome (Leigh et al 2011). Given the absence of a rigid cell wall, H. volcanii affords a cheap and simple protocol for carotenoid extraction compared with the lengthy and complicated extraction procedure from pink shrimp or carrot, which involves the use of expensive equipment (Mezzomo et al 2011;Rawson et al 2011;Zalazar et al 2019). Hence, by remodelling the carotenoid biosynthetic pathway through genetic engineering, production and extraction of β-carotene using H. volcanii may provide a more effective, efficient and affordable method of natural carotenoid synthesis than those currently offered by chemical synthesis route or by extraction route from other microbes, plants and algae.…”