Evaluating the effects of nanoparticles on biomass growth and astaxanthin accumulation in Haematococcus lacustris is crucial for optimizing the production of astaxanthin, a valuable carotenoid with numerous industrial applications. Identifying the life stages at which these nanoparticles exert stimulatory or toxic effects will aid in formulating effective production strategies. This study investigated the effects of titanium dioxide (TiO₂), zinc oxide (ZnO), and copper oxide (CuO) nanoparticles on biomass growth, astaxanthin biosynthesis, and lipid accumulation in Haematococcus lacustris, with a focus on their stage-specific impact throughout the algal life cycle. The nanoparticles were added at the start of cultivation, and the microalgal cultures developed continuously in their presence. Sampling for biochemical analyses was performed at distinct life stages (green motile, palmella, and aplanospore), enabling the assessment of stage-dependent responses. TiO₂NPs significantly stimulated biomass accumulation during the green motile stage. In the palmella stage, astaxanthin levels decreased in the presence of all nanoparticles, likely due to the absence of a stress signal required to activate pigment biosynthesis, despite ongoing biomass growth. In contrast, the aplanospore stage exhibited reactivation of astaxanthin biosynthesis and increased lipid accumulation, particularly under TiO₂NPs. Astaxanthin content increased by 21.57%. This study highlights that TiO₂, ZnO, and CuO nanoparticles modulate growth and astaxanthin biosynthesis in Haematococcus lacustris in a life cycle-dependent manner.

The purpose of this study was to examine the influence of 10 and 20 nm nanoparticles (AgNPs) on the growth and biochemical composition of microalga Porphyridium purpureum CNMN-AR-02 in two media which differ by the total amount of mineral salts (MM1 with 33.02 g/L and MM2 with 21.65 g/L). Spectrophotometric methods were used to estimate the amount of biomass and its biochemical composition. This study provides evidence of both stimulatory and inhibitory effects of AgNPs on different parameters depending on the concentration, size, and composition of the nutrient medium. In relation to the mineral medium, AgNPs exhibited various effects on the content of proteins (an increase up to 20.5% in MM2 and a decrease up to 36.8% in MM1), carbohydrates (a decrease up to 35.8% in MM1 and 39.6% in MM2), phycobiliproteins (an increase up to 15.7% in MM2 and 56.8% in MM1), lipids (an increase up to 197% in MM1 and no changes found in MM2), antioxidant activity (a decrease in both media). The composition of the cultivation medium has been revealed as one of the factors influencing the involvement of nanoparticles in the biosynthetic activity of microalgae.

Metal oxide nanoparticles, such as ZnONPs and TiO₂NPs, are increasingly applied in various industries. However, their effects on photosynthetic microorganisms at environmentally relevant concentrations remain poorly understood. This study evaluated the impact of ZnONPs and TiO₂NPs, at concentrations ranging from 0.1 to 30 mg/L, on the cyanobacterium Nostoc linckia (strain CNMN-CB-03), a species recognized for its adaptability and biotechnological potential. The nanoparticles were added to controlled cultures, and changes in biomass composition and pigment content were assessed using spectrophotometric assays. Both nanoparticle types significantly affected the physiological and biochemical profile of Nostoc linckia. Low concentrations of ZnONPs stimulated the accumulation of biomass, chlorophyll, carotenoids, and lipids, while higher doses caused a reduction in phycocyanin and in total phycobiliproteins content. TiO₂NPs consistently promoted biomass growth across all tested concentrations, with decrease in carotenoids and total phycobiliproteins observed at the highest concentrations. For both nanoparticle types, malondialdehyde (MDA) levels decreased compared to the control, indicating reduced oxidative stress and effective cellular adaptation. The results highlight the remarkable resilience and metabolic flexibility of Nostoc linckia in the presence of nanoparticles, supporting its potential as a biotechnological platform for the sustainable production of valuable metabolites under controlled stress conditions.

Background: Enhancing Forest seedling resilience and improving soil quality are critical challenges under current climate change conditions. Cyanobacterial exopolysaccharides (EPS) represent a promising biotechnological solution due to their capacity to improve water retention, stabilize soil structure, and modulate rhizosphere interactions, thereby supporting plant adaptation to abiotic stress. Material and Methods: The cyanobacterial strain Nostoc linckia CNMN-CB-03 was cultivated on a range of nutrient media to identify optimal conditions for EPS production. Key physicochemical parameters, including temperature, light intensity, and pH, were systematically optimized. EPS were isolated from the culture medium by ethanol precipitation, then dried to constant weight and formulated into a stable powder via spray drying. The resulting product was applied in a nursery experiment on oak seedlings using localized rhizosphere treatment (0.1 g/L), with untreated plants serving as controls. Results: Comparative evaluation of nutrient media identified MN-1 and BG-11 supplemented with NaHCO₃ as the most efficient systems for EPS biosynthesis, with MN-1 providing consistently higher yields under optimized conditions. Implementation of a stage-specific cultivation regime - 30°C and 60 μmol photons m⁻² s⁻¹ during the initial growth phase, followed by reduced temperature (25°C) and light intensity (35 μmol photons m⁻² s⁻¹), significantly enhanced EPS production, reaching up to 2.68±0.09 g/L after a 16-day cultivation cycle. The developed protocol proved robust and reproducible, integrating biomass cultivation, EPS recovery, and downstream processing into a coherent technological workflow. Spray drying enabled the production of a homogeneous, stable, and easily applicable powder suitable for field use. Nursery trials demonstrated that EPS application did not negatively affect seedling physiological status and contributed to maintaining root system integrity. Moreover, treated seedlings showed indications of improved rhizosphere conditions, likely related to enhanced soil moisture retention and structural stability. These effects are expected to translate into improved establishment rates and root regeneration capacity during the subsequent growing season. Conclusions: Nostoc linckia-derived EPS demonstrate strong potential as a sustainable biostimulant for forestry applications, supporting root protection and improving rhizosphere functionality. The developed technology is experimentally validated, scalable, and relevant for practical implementation in nursery and reforestation systems.

Background: Sulfated polysaccharides (SPS) are biopolymers located on cell surfaces and in the extracellular matrix of microalgae and cyanobacteria. They are known for antioxidant, antiviral, and immunomodulatory properties. Due to their high sulphation and polyanionic nature, SPS interact with plant cells as natural elicitors and biostimulants. Their application can enhance seed germination, stimulate root and shoot growth, improve nutrient uptake, strengthen defense responses, and increase tolerance to abiotic stress. These effects are relevant for tomato seedlings in the Czech Republic, which are vulnerable to low spring temperatures and to summer heat and drought stress. Aim of the study: The main objective of this study is to establish baseline methodologies and assess seed treatments with SPS biostimulants derived from Arthrospira platensis (spirulina), developed at IMB UTM, for enhancing tomato resilience to temperature extremes and water deficit, in relation to cumulative Growing Degree Days (GDD). Materials and methods: For this purpose, SPS were extracted from spirulina biomass using distilled water at a ratio of 1:45 (w/v) at 90 °C for 2 h, followed by centrifugation to remove residual biomass. The resulting supernatant was subsequently treated with cetyltrimethylammonium bromide to precipitate the polysaccharide fraction, purified, and redissolved in distilled water. Tomato seeds were treated with obtained SPS before sowing. Results: Under controlled greenhouse conditions, treated seeds exhibited faster, more synchronized emergence, with a reduction in mean germination time of approximately 2-3 days and a 25-35% increase in seedling vigor index compared to the untreated control. These responses were associated with enhanced root elongation and shoot growth. The most pronounced effects of the biostimulant application were observed at the seedling stage, where treated plants showed more vigorous and structurally balanced development, including a betterdeveloped root system and improved physiological readiness for transplanting. Although the risk of late-spring frosts constrained transplanting dates, seedlings were successfully transplanted into open-field conditions in the Elbe Lowland region of the Czech Republic. Following transplanting, treated plants demonstrated faster field establishment, characterized by more rapid root anchorage and an earlier resumption of growth. Moreover, biostimulanttreated seedlings exhibited increased tolerance to early-season environmental variability, particularly spring temperature fluctuations, resulting in reduced transplanting stress and improved early field performance. Conclusions: These findings highlight the relevance of SPS biostimulants for improving tomato development and adaptation to extreme temperature and water deficit.