Evaluation of halophilic microalgae isolated from Rabigh Red Sea coastal area for biodiesel production: Screening and biochemical studies

Photobiota of the Tropical Red Sea: Fatty Acid Profile Analysis and Nutritional Quality Assessments

Photosynthetic organisms are primary sources of marine-derived molecules, particularly ω3 fatty acids (FAs), which influence the quality of marine foods. It is reported that tropical organisms possess lower FA nutritional quality than those from colder oceans. However, the high biodiversity known for tropical areas may help compensate for this deficiency by producing a high diversity of molecules with nutritional benefits for the ecosystem. Here we addressed this aspect by analyzing the FA profiles of 20 photosynthetic organisms from the salty and warm Red Sea, a biodiversity hot spot, including cyanobacteria, eukaryotic microalgae, macroalgae, mangrove leaves, as well as three selected reef's photosymbiotic zooxanthellate corals and jellyfish. Using direct transesterification, gas chromatography-mass spectrometry, FA absolute quantification, and nutritional indexes, we evaluated their lipid nutritional qualities. We observed interspecific and strain-specific variabilities in qualities, which the unique environmental conditions of the Red Sea may help to explain. Generally, eukaryotic microalgae exhibited the highest nutritional quality. The previously unanalyzed diatoms Leyanella sp. and Minutocellus sp. had the highest eicosapentaenoic acid (EPA) contents. The bioprospected Red Sea photobiota exhibited pharmaceutical and nutraceutical potential. By sourcing and quantifying these bioactive compounds, we highlight the untapped rich biodiversity of the Red Sea and showcase opportunities to harness these potentials.

A polyphasic approach in the identification and biochemical characterization of Dunaliella tertiolecta with biodiesel potential from a saltern in Mauritius

Bioprospecting robust and oleaginous strain is crucial for the commercialization of microalgae-based biodiesel. In this study, a microalgal strain SCH18 was isolated from a solar saltern located in Mauritius. This isolate was identified as Dunaliella tertiolecta based on a polyphasic approach that combined molecular, physiological, and morphological analyses. Furthermore, the effect of different salinities on the biochemical composition and fatty acid profile of this microalga was investigated to explore its potential in producing biodiesel. Results from the growth studies showed that salinity of 1.0 M NaCl was optimal for achieving a high growth rate. Under this salt concentration, the growth rate and the doubling time were calculated as 0.39 ± 0.003 day-1 and 1.79 ± 0.01 days, respectively. In terms of biochemical composition, a substantial amount of carbohydrate (42.02 ± 5.20%), moderate amount of protein (30.35 ± 0.18%) and a low lipid content (17.81 ± 2.4%) were obtained under optimal NaCl concentration. The fatty acid analysis indicated the presence of palmitic acid, stearic acid, palmitoleic acid, oleic acid, linoleic acid, gamma, and alpha-linolenic acids, which are suitable for biodiesel synthesis. The predicted biodiesel properties were in accordance with the standard of ASTM 6751, indicating that the microalgal isolate D. tertiolecta SCH18 is a potential candidate for use in biodiesel production.

Cultivation of the polyextremophile Cyanidioschyzon merolae 10D during summer conditions on the coast of the Red Sea and its adaptation to hypersaline sea water

The west coast of the Arabian Peninsula borders the Red Sea, a water body which maintains high average temperatures and increased salinity compared to other seas or oceans. This geography has many resources which could be used to support algal biotechnology efforts in bio-resource circularity. However, summer conditions in this region may exceed the temperature tolerance of most currently cultivated microalgae. The Cyanidiophyceae are a class of polyextremophilic red algae that natively inhabit acidic hot springs. C. merolae 10D has recently emerged as an interesting model organism capable of high-cell density cultivation on pure CO2 with optimal growth at elevated temperatures and acidic pH. C. merolae biomass has an interesting macromolecular composition, is protein rich, and contains valuable bio-products like heat-stable phycocyanin, carotenoids, β-glucan, and starch. Here, photobioreactors were used to model C. merolae 10D growth performance in simulated environmental conditions of the mid-Red Sea coast across four seasons, it was then grown at various scales outdoors in Thuwal, Saudi Arabia during the Summer of 2022. We show that C. merolae 10D is amenable to cultivation with industrial-grade nutrient and CO2 inputs outdoors in this location and that its biomass is relatively constant in biochemical composition across culture conditions. We also show the adaptation of C. merolae 10D to high salinity levels of those found in Red Sea waters and conducted further modeled cultivations in nutrient enriched local sea water. It was determined that salt-water adapted C. merolae 10D could be cultivated with reduced nutrient inputs in local conditions. The results presented here indicate this may be a promising alternative species for algal bioprocesses in outdoor conditions in extreme coastal desert summer environments.