Divergent metabolic strategies in two Aphanothece species (Cyanobacteria): Interactive effects of temperature and light intensity on growth, pigment composition, and lipid profile

Abstract Temperature and light intensity are among the most influential environmental factors modulating cyanobacterial physiology, yet their interactive effects on metabolite accumulation remain understudied in several genera with biotechnological potential. In this study, the influence of temperature (12, 20 and 28 °C) and light intensity (60, 120 and 180 µmol photons m −2 s −1 ) on the growth, pigment profile, and lipid composition of two Aphanothece strains ( A. microscopica and A. stagnina ) was evaluated through a 3 2 full factorial design. Both species exhibited strain-specific responses across all measured parameters. In A. microscopica , high temperature and low light promoted the accumulation of chlorophyll a , phycobiliproteins (particularly phycocyanin and allophycocyanin), and a diversified carotenoid profile including echinenone and myxoxanthophyll. In contrast, A. stagnina showed higher pigment productivity under high temperature combined with high irradiance, particularly enriching zeaxanthin and β-carotene. Lipid content increased in both strains under low temperature and moderate light, suggesting a compensatory metabolic route under suboptimal growth conditions. Fatty acid analysis revealed major differences: A. microscopica displayed a complex profile dominated by palmitic acid and enriched with polyunsaturated fatty acids under cold treatments, while A. stagnina exhibited reduced diversity, with monounsaturated fatty acids, especially palmitoleic and myristic acids, prevailing under all conditions. These findings underscore the metabolic flexibility of Aphanothece species in response to environmental variation and highlight their differentiated potential for applications in biorefineries. Selective cultivation of each strain under tailored conditions may enhance the yield of specific pigments or lipids, supporting their use in biofuel, nutraceutical, and cosmeceutical industries. Graphical Abstract