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

Abstract

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.

Recent advances and fundamentals of microalgae cultivation technology

“…1 P [64] Nannochloropsis salina Influence of overexpression of the alcohol dehydrogenase from cyanobacterium Synechocystis sp. on adaptation to cold temperature.…”

“…This indicates that the species can thrive in low supplement conditions, making it a desirable choice for industrial use. [64] In order to increase the antioxidant enzymatic activity and enable cold adaptation of Nannochloropsis salina microalgae, transgenic overexpression of alcohol dehydrogenase from cyanobacteria was employed. [65] Galdieria sulphuraria, a thermoacidophile red alga that typically grows at 42 • C, was selected to grow at a lower temperature of 28 • C. [167] t growth or Remarkably, it took 250 days and 100 generations to develop a strain with temperature independent growth rate.…”

“…This indicates that the species can thrive in low supplement conditions, making it a desirable choice for industrial use. [ 64 ]…”

“…We categorized these findings according to the fundamental factors that regulate microalgae growth and properties including bioreactor type and supply of light and nutrients, [50][51][52] symbiotic microalgae-microbiotic interactions in which bacteria provide nitrogen fixation and nitrification as well as vitamins, whereas microalgae synthesize carbons, [53][54][55][56] CO 2 supplementation or genetic modifications of CO 2 fixation, [57][58][59][60] inorganic phosphate fixation, [61][62][63] adaptation to temperature. [64,65] Substantial research is focused on gene engineering and selection of microalga for food and pigment production. [36,[66][67][68] Additionally we discussed life cycle analysis (LCA) studies that examine the carbon footprint of the entire production process, including the design and operation of the facilities.…”

Modeling With Uncertainty Quantification Identifies Essential Features of a Non-Canonical Algal Carbon-Concentrating Mechanism

“…This species is extremophilic, with optimal laboratory growth conditions including low pH (~ 2) and high temperatures (~ 42 °C) (1,2). C. merolae and other thermo-acidophilic red algae draw interest for their unique biology and simple characteristics, which position them as useful model organisms and as candidates for biotechnology applications (3)(4)(5)(6). For example, C. merolae is of interest because it is one of few organisms which relies on photosynthesis in geothermal spring environments, where hot and acidic conditions restrict the availability of inorganic carbon and challenge biological carbon fixation (1,7).…”