Production of β-Phycoerythrin and Exopolysaccharide in Porphyridium purpureum Modulated via Static Magnetic Fields and Polymeric Nanofibers
Trade-offs between biomass productivity and metabolite accumulation constrain microalgae cultivation for high-value biomolecules due to nutrient competition and concurrent metabolic pathways. This study evaluated the independent and combined effects of static magnetic fields (SMF) and polymeric nanofibers on growth performance, biomass composition, and exopolysaccharide (EPS) profiles of Porphyridium purpureum. A process intensification strategy was applied by integrating external physical forcing and structured functional materials to enhance mass transfer and carbon utilization efficiency. Cultivations were conducted under controlled photobioreactor conditions using SMF exposure for 1 h d−1 or 24 h d−1, combined with polyacrylonitrile (PAN) nanofibers or monoethanolamine-functionalized nanofibers (MEA). Intermittent SMF increased maximal biomass concentration by 36% compared to the control, whereas continuous SMF, MEA nanofibers, and combined conditions reduced biomass accumulation by up to 45%. SMF promoted metabolic reallocation toward carbon-rich fractions, increasing released polysaccharides by 83% and lipid content by 38%. Nanofibers strongly enhanced pigment biosynthesis, with β-phycoerythrin reaching 41.3 mg g−1, threefold higher than the control. EPS characterization showed increased purity, uronic acid content, and sulfation depending on treatment. Overall, SMF and nanofibers acted as selective intensification tools, enabling tunable modulation of growth, metabolism, and product formation.