Enhanced carotenoid production in a novel Chlorella vulgaris isolate under nitrogen limitation: dynamics of pigment diversity across growth phases

Chlorella vulgaris is of significant biotechnology interest with broad applications in the production of valuable compounds such as carotenoids. Although extensively studied, comprehensive investigations of its pigment composition under nutrient stress are limited. This study presents a detailed biochemical and physiological analysis of a new C. vulgaris isolate, focusing on pigment diversity across different growth stages and varying nitrogen levels. After morphological and molecular identification, the isolate was cultivated in BG11 medium supplemented with different NaNO3 concentrations (1.5, 0.75, 0.375 and 0 g l−1). Growth kinetics, photosynthetic activity and pigment profiles were monitored throughout the cultivation period. Using high-performance liquid chromatography, a total of 12 pigments were identified, including some not commonly found in C. vulgaris, such as fucoxanthin and 19’-butanoyloxyfucoxanthin. Moderate nitrogen limitation (0.375 g l−1) led to a 43% increase in total carotenoid content without negatively affecting biomass yield or photosynthetic integrity. Under these conditions, levels of lutein, violaxanthin, fucoxanthin, zeaxanthin, α- and β-carotene were all enhanced, with lutein reaching a notably high content of 2.6 mg g−1 dry weight. Overall, our findings highlight the capacity of our new isolate to dynamically adjust its pigment composition in response to nutrient availability, particularly under nitrogen stress. This study provides detailed pigment data associated with different culture conditions supporting a cost-effective strategy for enhancing carotenoid yields and further substantiates the role of C. vulgaris as a sustainable source of functional ingredients for health and nutrition applications.