Impact of controlled light stress on intracellular and extracellular polysaccharide accumulation in Chlorella vulgaris cultivated in an system indoor of integrated photobioreactors

Chlorella vulgaris , a highly efficient unicellular photosynthetic organism, has gained attention as a sustainable source of biomass and bioactive compounds [ 1 ] due to its exceptional ability to utilize light and carbon dioxide, making it valuable for industrial and environmental applications. Recent research highlights the advantages of cultivating microalgae in closed indoor photobioreactors (PBRs), which allow precise control of light, temperature, and nutrients while minimizing water loss [ 2 ]. This controlled environment improves photosynthetic efficiency and allows deliberate stress induction to influence metabolite production. As a result, the decreasing cost of microalgal biomass is enabling cost-effective exploitation of valuable metabolites such as polysaccharides [ 3 ]. In this study, an system indoor of integrated photobioreactors designed to maximize microalgal production was used to cultivate C. vulgaris SAG 211-12 in modified BG-11 medium. This system comprised an acceleration module (three column PBRs of 8, 16, and 32 L) and a production module (three 150 L annular PBRs). Cultures were maintained for 14 days under three light intensities, and growth was monitored via optical density (OD), cell counts, and dry weight. Medium light produced the highest biomass, whereas high light intensity induced stress that increased extracellular polysaccharide (EPS) secretion but reduced intracellular polysaccharide (CHL-A) content. CHL-A was extracted with hot water, and EPS was isolated through filtration and dialysis. Chemical and morphological analyses revealed structural and compositional differences between CHL-A and EPS. Overall, both CHL-A and EPS derived from Chlorella vulgaris exhibit promising potential as natural ingredients for sustainable industrial applications of microalgal products, given that indoor cultivation enables year-round, uninterrupted production regardless of external environmental conditions, a significant advantage over higher plants, which typically yield bioactive compounds only during specific seasonal (balsamic) periods. Acknowledgment This study was carried out within the Agritech National Research Center and received funding from the European Union Next-Generation EU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D. 1032 17/06/2022, CN00000022). This research reflects only the authors’ views and opinions, neither the European Union nor the European Commission can be considered responsible for them. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany