<![CDATA[Graphical Abstract Highlight Research Chlorella sorokiniana achieved the highest cell density, growth rate, and biomass at 100 mg L⁻1 AMPEP. 100 mg L⁻¹ produced the largest cells, while higher concentrations (150–200 mg L⁻1) reduced cell density due to nutrient imbalances. 150 mg L⁻1 AMPEP maximized chlorophyll a and carotenoid accumulation, enhancing pigment production AMPEP demonstrated potential as a natural biostimulant to enhance microalgal productivity for biotechnological applications. Abstract Chlorella sorokiniana is a promising microalga valued for its production of pigments, lipids, and proteins with potential applications in biofuels, nutraceuticals, and pharmaceuticals. However, enhancing its growth and productivity remains a key challenge. Acadian Marine Plant Extract Powder (AMPEP), derived from the brown seaweed Ascophyllum nodosum, is known for its growth-promoting and stress-resistance properties in plants, but its effects on microalgae are not well understood. This study aimed to evaluate the effects of different concentrations of AMPEP (50, 100, 150, and 200 mg L⁻¹) on the growth, biomass, and pigment accumulation of C. sorokiniana. The experiment was conducted using a completely randomized design with five treatments (including a control) and three replicates per treatment. The results showed that 100 mg L⁻¹ AMPEP produced the highest cell density, with a 2.50-fold increase compared to the control, and the highest specific growth rate of 0.17 ± 0.03 day⁻¹. The largest cell size (19.51 ± 0.77 µm) was recorded at 200 mg L⁻¹, while biomass production peaked at 6.41 ± 0.49 g L⁻¹ with 50 mg L⁻¹. Maximum chlorophyll a and total carotenoid content were observed at 150 mg L⁻¹. Overall the 100 mg L⁻¹ AMPEP is the most balanced and optimal concentration overall for growth enhancement of C. sorokiniana, while other concentrations may be selected based on specific objectives like pigment or biomass production. These findings suggest that AMPEP, particularly at moderate concentrations, can significantly enhance the growth, biomass yield, and pigment content of C. sorokiniana. Further research is recommended to investigate the underlying mechanisms of AMPEP’s biostimulant effects and its potential application in large-scale algal cultivation systems.]]>
