Modulation of the metabolite content of the unicellular rhodophyte Porphyridium purpureum using a 2-stage cultivation approach and chemical stressors

Abstract

There have been growing interests in microalgal biotechnology for the biorefining of bioactive compounds such as carotenoid pigments, ω-3 fatty acids, antioxidants or antimicrobials for sectoral applications in the pharmacology, nutraceutical and cosmetic fields. This study focused on the unicellular marine rhodophyte Porphyridium purpureum CCAP 1380/1 A, which was cultivated via a two-stage batch growth mode for 10 days using hydrogen peroxide (H₂O₂), the phytohormone methyl jasmonate (MJ) and three plant extracts (Passiflora incarnata, Panax ginseng and Valeriana officinalis). The microalgal biomass was then analysed for its protein, phycoerythtin, carbohydrate and pigment composition together with its pigment content and antioxidant activity. Of note, MJ increased the protein and phycoerythtin content (up to 225 µg BSA eq./mg DW and 15 mg/ml, respectively) while both the MJ and H₂O₂ treatments increased carotenoid pigment yields (β-carotene and zeaxanthin, up to 5 and 4 mg/g, respectively). Carbohydrates were enhanced ∼10 fold by the Valeriana officinalis treatment (up 192 μg starch eq./mg). Overall, neutral lipids and antioxidants were mostly negatively affected by the plant extracts. The greatest antioxidant activity registered was obtained with the H₂O₂ treatment (15 μmol Trolox eq./g DW with TEAC assay). P. purpureum contains multiple valuable compounds of commercial interest. These results indicate that they can be favorably modulated using specific cultivation regimes and chemical enhancers, thereby facilitating the exploitation of the biomass by applying a suitable co-refinery pipeline.

Keywords: Antioxidants; Biorefinery; Microalgae; P. purpureum; Pigments; Zeaxanthin.