Arthrospira platensis, commonly known as Spirulina, is a photosynthetic filamentous cyanobacterium (blue–green microalga) that has been utilized as a food source since ancient times. More recently, it has gained significant popularity as a dietary supplement due to its rich content of micro- and macro-nutrients. Of particular interest is a water soluble phycobiliprotein derived from Spirulina known as phycocyanin C (C-PC), which stands out as the most abundant protein in this cyanobacterium. C-PC is a fluorescent protein, with its chromophore represented by the tetrapyrrole molecule phycocyanobilin B (PCB-B). While C-PC is commonly employed in food for its coloring properties, it also serves as the molecular basis for numerous nutraceutical features associated with Spirulina. Indeed, the comprehensive C-PC, and to some extent, the isolated PCB-B, has been linked to various health-promoting effects. These benefits encompass conditions triggered by oxidative stress, inflammation, and other pathological conditions. The present review focuses on the bio-pharmacological properties of these molecules, positioning them as promising agents for potential new applications in the expanding nutraceutical market.

Arthrospira platensis holds promise for biotechnological applications due to its rapid growth and ability to produce valuable bioactive compounds like phycocyanin (PC). This study explores the impact of salinity and brewery wastewater (BWW) on the mixotrophic cultivation of A. platensis. Utilizing BWW as an organic carbon source and seawater (SW) for salt stress, we aim to optimize PC production and biomass composition. Under mixotrophic conditions with 2% BWW and SW, A. platensis showed enhanced biomass productivity, reaching a maximum of 3.70 g L⁻¹ and significant increases in PC concentration. This study also observed changes in biochemical composition, with elevated protein and carbohydrate levels under salt stress that mimics the use of seawater. Mixotrophic cultivation with BWW and SW also influenced the FAME profile, enhancing the content of C16:0 and C18:1 FAMES. The purity (EP of 1.15) and yield (100 mg g⁻¹) of PC were notably higher in mixotrophic cultures, indicating the potential for commercial applications in food, cosmetics, and pharmaceuticals. This research underscores the benefits of integrating the use of saline water with waste valorization in microalgae cultivation, promoting sustainability and economic efficiency in biotechnological processes.

This study explores the mixotrophic cultivation of Limnospira platensis using dairy byproducts, specifically scotta whey (SW), buttermilk wastewater (BMW), and dairy wastewater (DWW), to promote biomass production and enhance the composition of bioactive compounds. By assessing various concentrations (1%, 2%, and 4% v v⁻¹) of these byproducts in a modified growth medium, this study aims to evaluate their effect on L. platensis growth, phycocyanin (C-PC) content, and fatty acid methyl ester (FAME) profiles. The results show that the optimal biomass production was achieved with 2% scotta and dairy wastewater, reaching maximum concentrations of 3.30 g L⁻¹ and 3.19 g L⁻¹, respectively. Mixotrophic cultivation led to increased C-PC yields, especially in buttermilk and dairy wastewater treatments, highlighting the potential for producing valuable pigments. Additionally, the FAME profiles indicated minimal changes compared to the control, with oleic and γ-linolenic acids being dominant in mixotrophic conditions. These findings support the viability of utilizing dairy byproducts for sustainable L. platensis cultivation, contributing to a circular bioeconomy while producing bioactive compounds of nutritional and commercial interest.

Background/Objectives: Natural polysaccharides have many bio-pharmacological effects, which make them compounds with potential in healthcare. Limnospira platensis (Spirulina), a well-known blue–green cyanobacterium with relevance in the market of nutraceuticals, produces polysaccharides with recognized antioxidant and anti-inflammatory activities. Noteworthy, the growth of the cyanobacterium biomass may be obtained in a more sustainable manner under mixotrophic conditions. In the present study, we compared the antioxidant and anti-inflammatory effects of polysaccharide-enriched extracts from the cyanobacterium cultured under autotrophism (Auto−P extract) or mixotrophism (Mixo−P extract); this latter was realized using medium added with brewery wastewater (BWW). Methods and Results: Non-cellular investigation showed a better antioxidant profile for Mixo−P extract in the OH radical scavenging assay and a similar activity between the extracts in ABTS and ferrous chelation assays. The antioxidant protective activity of L. platensis extracts investigated on HaCat cells in the range of 0.3–10 μg/mL (not cytotoxic concentrations), against hydrogen peroxide (H₂O₂, 600 μM)-induced damage, revealed a similar activity by the two extracts. When tested against the inflammatory stimuli with lipopolysaccharide (LPS, 10 μg/mL) or tumor necrosis factor-α (TNF-α, 10 ng/mL), both Auto−P and Mixo−P showed an ability to prevent the effects of the inflammatory agents on cell viability and on interleukin-1β (IL-1β) and interleukin-6 (IL-6) release, with a slightly greater potency by Mixo−P extract. Conclusions: In conclusion, our data suggest the possible use of L. platensis polysaccharide-enriched extracts in biological-made pharmaceuticals for skin disorders or in cosmeceuticals. In addition, this study demonstrates that mixotrophic cultivation of L. platensis may be an alternative and sustainable way for biotechnological applications of the cyanobacterium biomass.

This study explores the mixotrophic cultivation of Arthrospira platensis using dairy byproducts, specifically scotta whey (SW), buttermilk wastewater (BMW), and dairy wastewater (DWW), to promote biomass production and enhance the composition of bioactive compounds. By assessing various concentrations (1%, 2%, and 4% v v^-1) of these byproducts in a modified growth medium, the research aims to evaluate their effect on A. platensis growth, phycocyanin (C-PC) content, and fatty acid methyl ester (FAME) profiles. The results show that the optimal biomass production was achieved with 2% scotta and dairy wastewater, reaching maximum concentrations of 3.30 g L⁻¹ and 3.19 g L⁻¹, respectively. Mixotrophic cultivation led to increased C-PC yields, especially in buttermilk and dairy wastewater treatments, highlighting the potential for producing valuable pigments. Additionally, the FAME profiles indicated minimal changes compared to the control, with oleic and γ-linolenic acids being dominant in mixotrophic conditions. These findings support the viability of utilizing dairy byproducts for sustainable A. platensis cultivation, contributing to a circular bio-economy while producing bioactive compounds of nutritional and commercial interest.