Sustainable agriculture faces increasing challenges, necessitating innovative approaches to advance resource efficiency with minimal ecological consequences. One promising solution is nanobiotechnology, which takes advantage of natural systems for the eco-friendly synthesis of functional nanomaterials. Prokaryotic cyanobacteria and eukaryotic microalgae, due to their rapid growth, adaptability to diverse environments, and capacity for biosynthesis of valuable compounds, are model organisms highly suitable for medical, biotechnological, industrial, agricultural, and environmental applications. These photosynthetic microorganisms have demonstrated their efficacy in the biosynthesis of nanomaterials, which has potential benefits in various agricultural applications. The use of cyanobacteria- and microalgae-based nanomaterials in improving agricultural practices represents an emerging field of nanotechnology that requires ongoing research and responsible application management. To present a complete and timely foundation for this field, a systematic review of relevant research from the last five years was performed, exploring the contribution of cyanobacteria and microalgae to the advancement of nanobiotechnology as an efficient biotransformative tool for sustainable agriculture.

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: 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.

Background: Interactions between engineered nanoparticles (NPs) and photosynthetic microorganisms represent a rapidly developing field at the interface of nanotechnology and microbial biotechnology. Metal and metal oxide nanoparticles can act as both stressors and modulators of cellular metabolism, inducing oxidative stress responses that may lead to either growth inhibition or adaptive metabolic redirection. Aim of the study: The study aims to elucidate the physiological and biochemical responses of selected photosynthetic microorganisms (cyanobacteria and microalgae) to exposure to engineered nanoparticles, with a focus on oxidative stress modulation and its impact on biomass productivity and metabolite accumulation. Materials and methods: Model strains of cyanobacteria and microalgae (e.g., Arthrospira platensis, Nostoc linckia, Haematococcus lacustris) were cultivated under controlled laboratory conditions and exposed to metal and metal oxide nanoparticles of defined sizes and concentrations. Growth parameters, pigment content (chlorophylls, carotenoids), and oxidative stress markers were monitored. Spectrophotometric and biochemical assays were used to assess cellular responses, and comparative analyses between treatments and controls were performed. Results: Exposure to engineered NPs induced dose- and size-dependent responses across all tested strains. At higher concentrations, NPs inhibited growth, increased oxidative stress, degraded pigments, and impaired photosynthetic activity. In contrast, sublethal concentrations triggered hormetic effects, reflected in moderate stimulation of growth and metabolism. Photosynthetic microorganisms activated antioxidant defensemechanisms, leading to increased levels of protective pigments and improved redox balance. In Haematococcus lacustris, controlled nanoparticle exposure promoted a shift toward carotenoid biosynthesis, resulting in enhanced astaxanthin accumulation under moderate stress conditions. Cyanobacteria such as Arthrospira platensis and Nostoc linckia exhibited adaptive responses mediated by extracellular polymeric substances (EPS), which reduced nanoparticle bioavailability and toxicity. Nanoparticle size also influenced biological effects, with smaller particles inducing stronger responses. Overall, the results highlight the dual role of nanoparticles as both stressors and modulators of metabolism, with controlled oxidative stress enhancing the production of valuable metabolites. Conclusions: The results demonstrate that controlled nanoparticle-induced stress can be exploited as a biotechnological tool to modulate metabolic pathways in photosynthetic microorganisms. Understanding the balance between toxicity and hormesis is essential for developing sustainable biotechnological applications, including high-value metabolite production.

Background: Long-term preservation of Saccharomyces cerevisiae by lyophilization is highly important for scientific research and for the biotechnological and food industries. Maintaining cell viability and genetic stability is essential for reproducible results and consistent product quality. Lyophilization includes rapid freezing of microbial cultures followed by water removal through sublimation under vacuum. Therefore, pre-freezing temperature is a key factor affecting post-lyophilization survival, as it influences ice crystal formation, membrane integrity, and intracellular stability. Higher pre-freezing temperatures cause slower freezing and larger ice crystals, leading to irreversible cell damage and reduced viability. Lower temperatures ensure faster freezing, smaller and more uniform ice crystals, less mechanical injury, and higher survival rates. The aim of this study was to evaluate the influence of pre-freezing temperature and reactivation time on the survival capacity of Saccharomyces cerevisiae yeasts after 13 years of storage in a lyophilized state. Materials and methods: The study included 11 strains of Saccharomyces cerevisiae from the National Collection of Nonpathogenic Microorganisms of the Institute of Microbiology and Biotechnology, Technical University of Moldova, lyophilized in 2013 using skimmed milk as a protective agent. Prior freezing was performed at two temperature regimes: -50°C and -80°C. Cultures were reactivated with 1 mL of distilled water for 4 and 16 hours, and viability was assessed by colony-forming unit (CFU) counts, followed by logarithmic transformation of the data. Results: The results demonstrated that rapid freezing at -80°C led to higher cell viability, ranging from 38.2% to 67.8%, depending on the strain analyzed. The use of a higher prefreezing temperature (-50°C) was associated with a slightly reduced survival rate, with values between 33.0% and 67.1%. Additionally, standard reactivation (4 hours) resulted in low titers of 2.1-3.7 log₁₀ CFU·mL⁻¹. Under these conditions, optimization of reactivation parameters became necessary; extending the reactivation time to 16 hours led to a significant increase in yeast titers, reaching up to 6.8 log₁₀ CFU·mL⁻¹. Conclusions: This study demonstrates significant long-term survival of lyophilized yeast strains after 13 years of storage. Selecting an optimal pre-freezing temperature, such as -80°C, minimizes the negative effects associated with ice crystal formation, osmotic stress, and molecular instability, thereby enhancing the survival capacity of Saccharomyces cerevisiae strains. Furthermore, extended reactivation time significantly improves viability parameters, highlighting the importance of post-lyophilization recovery conditions.