Cultivation and physiological characterization of a desert-derived Halospirulina isolate

Here, we describe a filamentous Halospirulina isolate (Halospirulina saudiensis) obtained from water-clay microhabitat the Empty Quarter desert, (ar-Rub al-Kh[a]l[i]), Saudi Arabia which grows in saline conditions. We present its fully sequenced genome, the first for the genus, and characterize its growth dynamics as well as biochemical composition under a range of cultivation conditions. Protein, carbohydrate, lipid, and phycocyanin content varied with cultivation regime but were largely stable. H. saudiensis reached biomass concentrations of up to 9.83 g L-1 at pH 7, 35 {degrees}C and continuous 325 {micro}mol photons m-2 s-1. Variable climate simulations in lab-scale photobioreactors revealed preference for warmer season cultivation under modeled outdoor conditions. Carotenoid analysis revealed a pigment profile enriched in canthaxanthin and other ketocarotenoids, distinguishing it from industrial Limnospira and positioning its value for neutraceuticals and feed additives. Genome analysis identified a carotene ketolase (crtO) homolog consistent with other cyanobacteria that accumulate ketocarotenoids. Phycocyanin content was heavily dependent on culture health and varied with cultivation pH, irradiance, reaching maximum values of 67.3 {+/-} 0.8 mg gDW-1 (6.73 %). Extracted phycocyanin showed marginal thermal stability compared to that from L. platensis. The findings suggest that H. saudiensis could be a promising source of biomass, ketocarotenoids, and natural pigments, cultivated in saline conditions with elevated temperature and irradiance. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=71 SRC="FIGDIR/small/728284v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@17d6143org.highwire.dtl.DTLVardef@7cb1f7org.highwire.dtl.DTLVardef@880df4org.highwire.dtl.DTLVardef@4c16a6_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIHalospirulina saudiensis sp. nov. isolated from Empty Quarter C_LIO_LIFirst genome-resolved characterization of a Halospirulina strain C_LIO_LIReached 9.83 g L-1 in Red Sea salinity conditions C_LIO_LIAccumulates canthaxanthin as major carotenoid C_LIO_LIPhycocyanin slightly thermotolerant C_LI