Iron bioaccessibility assessment and bioaccumulation enrichment in microalgae under different production conditions

Iron-deficiency anemia is a major global health issue impacting approximately 1 billion people worldwide. Microalgae are sustainable and iron-rich resources; however, comprehensive studies on the bioaccessibility and bioaccumulation of microalgae-derived iron are limited. This study assessed these factors using three different microalgae species (Arthrospira platensis, Galdieria sulphuraria, and Chlorella vulgaris) grown under autotrophic, heterotrophic, and mixotrophic conditions using both standard (all modes) and iron-enriched media (autotrophic mode only). With the standard medium, the highest levels of iron bioaccumulation were observed under autotrophic conditions for A. platensis (563.4 mg/kg) and C. vulgaris (326.5 mg/kg), whereas G. sulphuraria reached its peak accumulation (238.9 mg/kg) under mixotrophic conditions. Heterotrophic mode yielded superior bioaccessibility results (66.9% for G. sulphuraria and 76.3% for C. vulgaris) compared to autotrophic cultivation (18.4%, 39.8%, and 41.8% for A. platensis, G. sulphuraria, and C. vulgaris, respectively). Increased iron concentrations in the culture medium resulted in substantial enhancements in iron bioaccumulation, particularly for G. sulphuraria. A 7.6-fold increase (up to 1,472.4 mg/kg) was achieved with a 150-fold iron concentration in the medium under autotrophic conditions. However, this increase in biomass iron content was accompanied by a relative decline in bioaccessibility, from 36.8% to 17.1%. The maximum amount of absolute bioaccessible iron (251.6 mg/kg) was found in G. sulphuraria cultivated autotrophically, which considerably exceeds the levels typically found in conventional foods. This study systematically evaluated the bioaccessibility and bioaccumulation of iron in various microalgae species, highlighting their potential as sustainable, innovative, highly bioaccessible, and iron-rich sources for addressing iron-deficiency anemia.