Innovative exopolysaccharide-based hydrogel for controlled phycoerythrin release: Synthesis and characterization

This study optimizes B-phycoerythrin accumulation in Porphyridium sp. using Box-Behnken design, achieving a remarkable 3.34-fold increase over standard culture conditions with an F/2 culture medium. The maximum B-phycoerythrin production level of 4.71 ± 0.075 % (w/w) was observed with 37 g/L NaCl, 8.6 g/L MgCl₂·6H₂O, and 1.625 g/L CaCl₂. B-phycoerythrin demonstrated notable in vitro antioxidant properties and potent antibacterial activity against Pseudomonas aeruginosa PAO1 (MIC = 100 μg/mL), Listeria monocytogenes ATCC 19117 (MIC = 50 μg/mL), Salmonella enterica ATCC 14028 (MIC = 50 μg/mL), Staphylococcus aureus ATCC 6538 (MIC = 50 μg/mL), and Escherichia coli ATCC 8739 (MIC = 100 μg/mL). Concurrently, extracted and characterized exopolysaccharide (EPS) from Porphyridium sp. was found to be primarily composed of galactose (40.09 %), xylose (36.80 %), glucose (16.65 %), and glucuronic acid (4.76 %), according to structural analysis. This EPS was then used to create hydrogel through crosslinking with sodium trimetaphosphate (STMP). The resultant hydrogel as well as the exopolysaccharide were evaluated for their free swelling capacity, centrifuge retention and absorption under compression capacities, and results showed excellent free swelling capacity. The release behavior of B-phycoerythrin from the hydrogel was investigated at two pH levels 5.5 and 7.4, revealing a lower cumulative release at pH 7.4. The release pattern was best described by the Higuchi model. These findings indicate that the exopolysaccharide-STMP hydrogel possess significant potential for drug delivery applications, particularly in the controlled release of therapeutic agents.