Factors Influencing Phycocyanin Synthesis in Microalgae and Culture Strategies: Toward Efficient Production of Alternative Proteins

Global population growth makes an increase in food production inevitable, and protein plays a vital role as an essential nutrient. However, as the proportion of land used for agriculture and animal protein production decreases, the search for sustainable, low-cost alternatives to proteins has become a research priority. Microalgae can synthesize a wide range of proteins, among which phycocyanin is of interest due to its unique biological activity. It has a complete amino acid profile, contains essential amino acids, and is a high-quality source of protein. Most of the existing studies have focused on single influencing factors, improved methods, or specific culture conditions for the synthesis of phycocyanin in microalgae and have not yet analyzed the culture conditions, influencing factors, and improved strategies for the synthesis of phycocyanin in microalgae in a systematic and integrated manner, and the studies lacked comprehensiveness and consistency. In this paper, the key factors, mechanisms of action, and improvement strategies affecting the accumulation of phycocyanin in microalgae are reviewed. The growth of microalgae under autotrophic, heterotrophic, and mixed culture conditions and their effects on phycocyanin synthesis were systematically described. The aim is to accelerate the application of phycocyanin in the food industry and alternative proteins by improving the production efficiency of microalgae, promoting their comprehensive utilization, and injecting a new impetus into the development of a sustainable protein industry.