Microalgae offer a sustainable platform for biotechnology due to their rapid growth and ability to accumulate high-value metabolites such as lipids, proteins, and carbohydrates. This study investigates the biochemical and morphological responses of Chlorella vulgaris and Scenedesmus incrassatulus across different growth phases and under nitrogen (N) and phosphorus (P) deficiency. Molecular identification and phylogenetic analysis confirmed the taxonomic status of both species. Scanning Electron Microscopy (SEM) combined with Energy Dispersive X-ray Spectroscopy (EDS) revealed species-specific surface structures and elemental composition. S. incrassatulus exhibited a compact, granular morphology, while C. vulgaris showed a smoother, colonial structure. EDS analysis demonstrated higher potassium and phosphorus levels in C. vulgaris, whereas S. incrassatulus presented elevated calcium and magnesium contents. Biochemical profiling indicated a metabolic shift during the stationary phase, with reduced protein synthesis and increased lipid and carbohydrate accumulation. Under nitrogen deficiency, C. vulgaris achieved the highest lipid content (53.68%), while S. incrassatulus reached 45.86%. Carbohydrate accumulation was also prominent during the stationary phase, with values of 49.18% for C. vulgaris and 47.99% for S. incrassatulus. Protein content was highest in the exponential phase and declined under nutrient stress. Elemental analysis via Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) confirmed species-specific macronutrient and trace element profiles, supporting EDS data. These findings highlight the adaptive biochemical and structural traits of the two microalgae species, reinforcing their potential in biofuel production, sustainable agriculture, bioremediation, and environmental applications. Future work should focus on optimizing cultivation conditions and exploring genetic approaches to maximize metabolite yields for industrial-scale applications.

This study evaluates the phenolic content, antioxidant, and antibacterial properties of hydro-ethanolic extracts from six medicinal and aromatic plants in Morocco: Eucalyptus torquata, Thymus broussonetii, Lavandula angustifolia, Rosmarinus officinalis, Ziziphus lotus, and Acacia raddiana. Sonication was employed for extraction. Total phenolic content, total flavonoid content, and condensed tannin content were quantified using the Folin-Ciocalteu, aluminum chloride, and hydrochloric acid assays, respectively. Antioxidant capacity was assessed via DPPH, total antioxidant capacity, ferric reducing antioxidant power, and ABTS assays. Antibacterial activity was measured by the microdilution method. Phytochemical analysis revealed that E. torquata and Z. lotus had the highest total phenolic content, with 86.75 and 87.58 mg GAE/g of dry matter, respectively. T. broussonetii and R. officinalis had the highest flavonoid and condensed tannin content, at 297.12 mg QE/g of dry matter and 5.10 g/L, respectively. E. torquata exhibited the strongest antioxidant activity, with DPPH and ABTS values of 0.048 and 0.11 mg/mL, and a ferric reducing antioxidant power value of 209.375 mg/g. R. officinalis showed the highest total antioxidant capacity at 1.03 mg AAE/g of dry matter. All extracts displayed bactericidal effects. R. officinalis demonstrated the most potent antibacterial activity, with minimum inhibitory concentrations ranging from 0.625 to 5 mg/mL and minimum bactericidal concentrations from 1.25 to 10 mg/mL. High phenolic content and significant antioxidant activity were noted in E. torquata and R. officinalis. Additionally, all extracts showed substantial antibacterial activity against four bacterial strains, with R. officinalis being the most effective.