An integrated process for enhanced production and purification of fucoxanthin and sulfated polysaccharides in diatom Hyalosynedra toxoneides cultures

Background: This study explores the efficient production and purification of health-promoting compounds, fucoxanthin and sulfated polysaccharides, from the diatom Hyalosynedra toxoneides, contributing to the growing demand for sustainable bioactive compounds. Methods: Semi-continuous cultivation of H. toxoneides (AQ9) in three medium concentrations (2.5f, 5f, 10f) was conducted in a custom-made photobioreactor. Fucoxanthin was extracted using 95 % ethanol, purified through silica gel chromatography, and characterized via high-performance liquid chromatography. Crude polysaccharides were obtained, purified using DEAE-Sephacel resins, and characterized for uronic acid and sulfate content. Significant findings: Higher culture medium concentrations led to increased biomass, fucoxanthin, and polysaccharide yields, providing insights for large-scale cultivation. With a 10f medium in semi-continuous cultures, we achieved the highest yields of approximately 1.18 g/L for cell mass, 4.45 mg/L for fucoxanthin, and 17.20 mg/L for crude polysaccharides, with corresponding productivities of 0.20 g/L/day, 0.74 mg/L/day, and 2.46 mg/L/day. Fucoxanthin was purified from crude pigments with 91 % purity and 70 % recovery. Meanwhile, two uncharacterized sulfated polysaccharides were isolated from crude polysaccharides using anion-exchange chromatography. Notably, the culture media influenced sulfated polysaccharide distribution. This integrated approach contributes to efficient production and purification of bioactive compounds from diatom cultures, with potential applications in diverse industries, including nutraceuticals and cosmetics.