Storage stability of phycobiliproteins in a hydroalcoholic solution evaluated by an optical method

The aim was to evaluate the stability of pigments of the phycobiliprotein group extracted from the biomass of the Spirulina (Arthrospira) platensis cyanobacterium and the Porphyridium purpureum red microalgae. Water extracts of phycobiliproteins were obtained following a double freezing of the raw biomass of Arthrospira platensis and Porphyridium purpureum. An extraction was carried out with a phosphate buffer (0.05 M, pH = 7) in the cold (5 °C) for 24 hours. To the extracts obtained, 96% ethanol was added until its concentration in the solution was 20%. The hydroalcoholic extracts of phycobiliproteins were stored for three months. Pigment concentrations were monitored by an optical method. The allophycocyanin pigment demonstrated the highest storage stability. The highest degradation rate of phycobiliproteins was observed during their storage in the light at room temperature. The degradation rate of pigments under these conditions was 9and 80-fold higher (for B-phycoerythrin and C-phycocyanin, respectively) than similar indices during their storage in the dark and in the cold. C-phycocyanin was the least stable, compared to other studied phycobiliproteins. Its degradation rate under all storage options was 5to 10-fold higher than that of B-phycoerythrin under similar conditions. An essential conservation requirement for C-phycocyanin and β-phycoerythrin in hydroalcoholic solutions was the absence of light. For C-phycocyanin, a low temperature was necessary as well. Storage of B-phycoerythrin in the dark at room temperature is acceptable. These conditions can ensure the conservation of up to 86% of pigments in hydroalcoholic solutions for 25–30 days.