Characterization and exploration of biological properties of phycobiliproteins purified from Thai karstic cave cyanobacterium Nostoc sp. SW02

Abstract

Phycobiliproteins are colored water-soluble proteins found in cyanobacteria with potential applications in food and pharmaceuticals. Phycobiliproteins extracted from the Thai karstic cave cyanobacterium Nostoc sp. strain SW02 were purified, and their biological properties were characterized. Scale-up cultivation for 12 days revealed that maximum biomass and phycobiliproteins producing yield were 1.53 g/L and 31.92%, respectively. After purification, phycoerythrin was obtained as the principal component of phycobiliproteins, with a purity index up to 2.62, sufficient to be considered food and cosmetic grade. Native and SDS-PAGE analysis displayed that purified phycoerythrin and phycocyanin contained the αβ-subunits in hexamer form. Purified phycobiliproteins had a more stable structure and functionality in pH range 5.0–7.0, were resistant to strong oxidizers, and could withstand temperatures up to 60 °C. They also exhibited DPPH scavenging capabilities comparable to standard ascorbic acid. Pathogenic bacterial inhibition (MIC 250 μg/mL) and anticancer activity against the human HeLa cancer cell line (IC50 140 μg/mL) were also observed. With these prospective characteristics, phycobiliproteins obtained from Nostoc sp. SW02 have biotechnological value for biomedical research and also as a natural colorant for food and cosmetic applications.