Cyanobacterial pigments have attracted considerable attention in industry due to their bioactive potential and natural origin. In the present study, the growth dynamics and pigment composition, in terms of chlorophyll a, total carotenoids and phycobiliprotein content, of four cyanobacterial strains isolated from thermal springs, namely Oscillatoria subbrevis CZS 2201, Phormidium ambiguum CZS 2205, Nostoc calcicola TSZ 2203, and Synechococcus sp. CZS 2204, were investigated. The analysis revealed that the maximum quantity of chlorophyll a and total carotenoids was observed in Oscillatoria subbrevis CZS 2201 (26.49 and 3.44 µg mL⁻¹), followed by Phormidium ambiguum CZS 2205 (18.64 and 2.32 µg mL⁻¹), whereas a minimum amount was detected in Synechococcus sp. CZS 2204 (12.13 and 1.24 µg mL⁻¹), respectively. In addition, Oscillatoria subbrevis CZS 2201 showed higher quantity of phycobiliproteins, especially C-phycocyanin (45.81 mg g⁻¹), C-phycoerythrin (64.17 mg g⁻¹) and C-allophycocyanin (27.45 mg g⁻¹). Moreover, carotenoid derivatives of Oscillatoria subbrevis CZS 2201 were also identified, among which β-carotene was the dominant form (1.94 µg mL⁻¹), while the accumulation of zeaxanthin and myxoxanthophyll was relatively high (0.53 and 0.41 µg mL⁻¹, respectively) compared with echinenone and cryptoxanthin (0.34 and 0.23 µg mL⁻¹, respectively). The study revealed that Oscillatoria subbrevis CZS 2201 was a potent producer of secondary carotenoids, including myxoxanthophyll.

Photosynthetic prokaryotes known as cyanobacteria produce an extensive range of primary and secondary metabolites that serve multiple biotechnological and biomedical purposes. The non-model filamentous Phormidium species capture researchers’ attention through their biotechnological potentials from diverse metabolites and their ability to thrive in tough environments while producing bioactive compounds. In this study, a thermotolerant strain of Phormidium ambiguum was isolated from the Chundzha thermal springs in southeastern Kazakhstan and characterized morphologically, physiologically, and biochemically. This cyanobacterium demonstrated fast growth in its culture media along with significant accumulation of proteins (44.8% DM), carbohydrates (45% DM), and photosynthetic pigments like chlorophyll a and valuable carotenoids, including b-carotene, myxoxantophyll and zeaxanthin. The LC-ESI-MS/MS analysis of cyanobacterial non-polar extract identified 150 potential metabolites which include fatty acid derivatives, terpenoids and carotenoid-related compounds known for their antioxidant and antimicrobial properties, as well as immune system stimulation. Biological assays confirmed a weak antioxidant capacity in the DPPH test, while in immunological assays, the extract of P. ambiguum stimulated T lymphocyte proliferation and activation, as well as NK cell proliferation in vitro. It also exhibited moderate antibacterial activity towards tested Gram-negative and Gram-positive bacterial strains. While additional studies are required to address environmental robustness, biosynthetic regulation, and practical scalability, the present findings indicate that P. ambiguum represents a valuable non-model cyanobacterium for exploratory bioprospecting. Its metabolite profile and observed bioactivities support further investigation of this thermotolerant strain as a potential source of immunomodulatory, antioxidant, and antimicrobial compounds under controlled conditions.

Total lipids and fatty acid composition of five novel cyanobacterial species were studied and their differences were studied for potential biodiesel application.

The diversity of cyanobacteria from four hot springs in the Chundzha settlement, located in the Almaty region, was studied to determine the species composition and isolate axenic cultures of thermophilic cyanobacteria. The objective was to investigate the diversity, morphological and cultural properties of thermophilic cyanobacteria from the Chundzha hot springs, and to establish axenic cultures for potential utilization in biotechnology, as these organisms are scientifically interesting and valuable as a source of thermostable biomolecules. As a result of the study, eight axenic cyanobacteria cultures were isolated and identified as Oscillatoria subbrevis, Phormidium ambiguum, Nostoc commune, Synechococcus elongatus, Synechocystis sp., Tolypothrix tenuis, Anabaena cylindrica and Spirulina fusiformis. Optimal cultivation conditions were also determined: the isolated cyanobacteria cultures exhibited high growth rates when cultivated in BG-11, Zarruk, and Gromov nutrient media at an optimal temperature of 28-36°C, pH 7, and a light intensity of 50 µmol photons m−2s−1. Key words: hot springs, thermophiles, cyanobacterial diversity, isolated axenic cultures, morphological and cultural properties, selection of cultivation conditions, dynamics of growth.