Flow cytometry-assisted optimization of culture conditions for the PCP-containing dinoflagellate Heterocapsa pygmaea: effects on cell growth and pigment fluorescence

Abstract Dinoflagellates are promising sources of high-value light-harvesting proteins, but their commercial utilization remains limited by insufficiently optimized cultivation conditions and the lack of efficient physiological monitoring tools. This study aimed to enhance cell growth and peridinin–chlorophyll a–protein (PCP) performance in Heterocapsa pygmaea through a combined cultivation and monitoring framework. PCP was characterized using SDS-PAGE and HPLC, and environmental (temperature and light intensity) and nutritional (phosphorus, nitrogen, and iron) factors were systematically evaluated, with flow cytometry applied to simultaneously assess cell density and intracellular fluorescence intensity as a rapid in vivo indicator of PCP-associated physiological performance. The PCP preparation exhibited a molecular weight of 10–15 kDa and a pigment composition dominated by peridinin and chlorophyll a. The best-performing cultivation conditions within the tested ranges were 24°C, 100 µmol photons m⁻² s⁻¹, 60 µM phosphorus supplied as mixed sources, nitrate or mixed nitrogen conditions, and 17.55 µM iron. Incorporation of these parameters into a modified C5 medium significantly improved cell growth and fluorescence responses compared with conventional f/2 and K media (p < 0.05). Combining cultivation optimization with flow cytometry-guided physiological monitoring is an effective strategy for improving PCP-associated fluorescence responses and establishes a scalable framework for dinoflagellate bioprocess development and industrial biotechnology applications.