Haloferax mediterranei Cells as C50 Carotenoid Factories

Abstract

Haloarchaea produce C50 carotenoids such as bacterioruberin, which are of biotechnological in-terest. This study aimed to analyze the effect of different environmental and nutritional conditions on the cellular growth and dynamics of carotenoids accumulation in Haloferax mediterranei. The maximum production of carotenoids (40 µg·mL−1) was obtained during the stationary phase of growth, probably due to nutrient-limiting conditions (one-step culture). By seven days of culture, 1 mL culture produced 22.4 mg of dry weight biomass containing 0.18 % (w/w) of carotenoids. On the other hand, carbon-deficient cultures (low C/N ratio) were observed to be optimum for C50 bacterioruberin production by Hfx. mediterranei, but negatively affected the growth of cells. Thus, a two-steps process was evaluated for optimum carotenoids yield. In the first step, a nutri-ent-repleted culture medium enabled the haloarchaea to produce biomass, while in the second step, the biomass was incubated under osmotic stress and in a carbon-deficient medium. Under the conditions used, the obtained biomass contained 0.27% (w/w) of carotenoids after seven days, which accounts for 58.49 µg·mL−1 of carotenoids for a culture with turbidity 14.0.

Ubiquitousness of Haloferax and Carotenoid Producing Genes in Arabian Sea Coastal Biosystems of India

“…A significant difference in the G + C content was observed between Haloarchaeal and Halobacterial isolates (Epps-singleton p = 6.3427 × 10 −12 ) in line with the results reported in the literature [ 18 , 19 ]. The G + C content for 86.95% of the Haloarcheal isolates was above 60%, whereas only 36.36% of Halobacteria had G+C contents above 60% ( Figure S2d,e ).…”

“…On the contrary, extreme halophilic archaea encoded cruF, thus indicating potential bacterioruberin production. The predominant archaeal genus Halorubrum and Haloferax have also been reported to produce bacterioruberin [ 19 , 41 , 42 ]. The wide prevalence of cruF among the dominant archaeal genera strengthens the potential to harness bacterioruberin from the coastal biosystems.…”

“…Haloarcheal red pigments are mainly astaxanthin and bacterioruberin, while orange pigments could be salinixanthin [ 6 , 37 ]. Both pigment types have significant antimicrobial and antioxidant properties [ 6 , 19 , 43 , 44 ]. Yellow pigments of haloarchaea are compounds such as 4,4’-diaponeurosporene, zeaxanthin, or lutein with applications in food colorants, visual acuity, and antibacterial activity against multidrug-resistant organisms [ 45 , 46 ].…”

“…Nevertheless, the sediment in the shallow coastal environment is exposed to similar UV radiation and higher salinity. Carotenoid pigments such as bacterioruberin are known to provide metabolic balance via osmoregulation and oxidation stress, respectively, when exposed to salinity and UV radiation [ 18 , 19 , 20 , 21 ]. Despite the differences between the open sea and coastal region, there is no in-depth comparative study on the diversity of pigmented halophiles to the best of our knowledge.…”

Assessment of Haloferax mediterranei Genome in Search of Copper-Molecular Machinery With Potential Applications for Bioremediation

“…One of the haloarchaeal species of particular interest from a biotechnological point of view is Haloferax mediterranei ( Rodriguez-Valera et al, 1983 ). Among its most prominent industrial applications, it must be highlighted as a model producer of polyhydroxyalkanoates (PHA), due to its high yield and easy extraction by osmotic shock ( Wang and Zhang, 2021 ); as a source of hydrolytic enzymes like lipases ( Akmoussi-Toumi et al, 2018 ); and as a cell factory for carotenoids production like bacterioruberin ( Giani et al, 2021 ). By serendipity, the function of the CRISPR system was first elucidated from this species, by Mojica and co-workers, appearing published for the first time in 2005 ( Mojica et al, 2005 ).…”