Abstract
A novel freshwater strain of Coelastrella multistriata MZ–Ch23 was discovered in Tula region, Russia. The identification is based on morphological features, phylogenetic analysis of SSU rDNA gene and ITS1–5.8S rDNA–ITS2 region and predicted secondary structure of the ITS2. Phylogenetic analysis places the novel strain in the “core” Coelastrella clade within the Chlorophyceae. This is the first record of Coelastrella multistriata in the algal flora of Russia. Cultivation experiments were carried out to evaluate growth dynamics of the newly identified strain and the impact of nitrogen and/or phosphorus depletion on the fatty acid profiles and lipid productivity. On the fully supplemented Bold’s basal medium and under phosphorus-depleted conditions as well, the fatty acid profiles were dominated by α-linolenic acid (29.4–38.1% of total fatty acids). Depletion of either nitrogen or both nitrogen and phosphorus was associated with increased content of oleic acid (32.9–33.7%) and linoleic acid (11.9%). Prolongation of the growth to two months (instead of 25 days) resulted in increased content and diversity of very long-chain fatty acids including saturated species. The total very long-chain fatty acid content of 9.99% achieved in these experiments was 1.9–12.3-fold higher than in stress experiments. The highest variation was observed for oleic acid (3.4–33.7%). The novel strain showed the ability to accumulate lipids in amounts up to 639.8 mg L−1 under nitrogen and phosphorus starvation, which exceeds the previously obtained values for most Coelastrella strains. Thus, the newly identified MZ–Ch23 strain can be considered as a potential producer of omega-3 fatty acids on fully supplemented Bold’s basal medium or as a source of biomass with high content of saturated and monounsaturated fatty acids after nitrogen and phosphorus starvation.
Highlights
The green microalgae genus Coelastrella Chodat (Scenedesmaceae, Sphaeropleales) is characterized by highly variable morphology, which complicates species identification[1,2,3]
Algae are among the first organisms to colonize anthropogenically disturbed habitats, thanks to their extreme ecological plasticity and ability to withstand the negative impact of extreme environmental c onditions[17,18,19]
Pyrenoid is single with a sheath of several large starch grains
Summary
The green microalgae genus Coelastrella Chodat (Scenedesmaceae, Sphaeropleales) is characterized by highly variable morphology, which complicates species identification[1,2,3]. The great demand for polyunsaturated fatty acids, notably the long-chain omega-3 species (eicosapentaenoic, docosahexaenoic, and α-linolenic), is due to their relevance to human health, with multiple neutralizing functions and pharmacological actions[14]. Algae strains capable of synthesizing high amounts of omega-3 fatty acids are much sought after. Optimized protocols of their cultivation will contribute to balanced diets for humans, by provision of feeds and supplements for agriculture and aquaculture. To assess biotechnological potential of the new strain, experiments were carried out to determine the optimal cultivation conditions and variability of the fatty acid profiles as a function of growth medium composition
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