Comparison of C-phycocyanin from extremophilic Galdieria sulphuraria and Spirulina platensis on stability and antioxidant capacity

Abstract C-phycocyanin is a natural blue-colored biliprotein with various biological activities. Commercial C-phycocyanin from Spirulina platensis has poor stability, which severely limits its application in food, medicine, cosmetics, and other industries. Extremophilic red algae Galdieria sulphuraria is found in hot springs with a pH of 1–3 and temperature above 40 °C. Hence, C-phycocyanin from G. sulphuraria has the potential to withstand high temperatures. This study aimed to compare the stability of C-phycocyanins from G. sulphuraria and S. platensis under different pH, temperature, stabilizer concentration, and light conditions. The results showed that C-phycocyanin from G. sulphuraria was more stable than that from S. platensis under all conditions, especially in the range of 50–65 °C, and in neutral environment of pH 7. After 30 min incubation at 60 °C and pH 7, the color preservation rate of C-phycocyanins from G. sulphuraria and S. platensis were 86.66% and 60.83%, respectively. The kinetic analysis revealed that under the influence of the stabilizer, the stabilities of both phycocyanins were improved. However, C-phycocyanin from G. sulphuraria obtained the highest mid-unfolding temperature of 73.00 °C compared with 69.81 °C for that of C-phycocyanin from S. platensis. In addition, the antioxidant capacity of two phycocyanins was similar. Therefore, C-phycocyanin from G. sulphuraria is an excellent alternative to the current commercial C-phycocyanin.