Phenoloxidase activation, antimicrobial, and antibiofilm properties of β-glucan binding protein from Scylla serrata crab hemolymph

Abstract In this study, we purified β-GBP from hemolymph of Scylla serrata crabs using affinity chromatography. The purified S . serrata β-GBP ( Ss -β-GBP) had 100 kDa molecular mass in the SDS-PAGE. MALDI-TOF/TOF analysis was conducted, revealing that the purified 100 kDa protein had 96% similarity with β-GBP of Astacus leptodactylus . Ss -β-GBP was characterized using high-performance liquid chromatography (HPLC), X-ray diffraction (XRD) analysis, circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy, which confirmed the structure of the Ss -β-GBP. The purified Ss -β-GBP was functionally analyzed by yeast agglutination and phagocytic reaction assays. Moreover, the PO enhancing ability of Ss -β-GBP was evidenced through PO activity. Specifically, the antibacterial activity of the Ss -β-GBP against Gram-positive ( Enterococcus faecalis and Staphylococcus aureus ) and Gram-negative ( Escherichia coli and Pseudomonas aeruginosa ) bacteria was evaluated by determining its minimum inhibitory concentration (MIC)  Ss -β-GBP at 50 and 100 μg/ml was outlined using light microscopy and confocal laser scanning microscopy (CLSM). Bacterial viability assays also outlined the dose-dependent activity of Ss -β-GBP based on the ratio of live/dead bacterial cells. The results of this study revealed that crab-borne Ss -β-GBP might be widely used to suppress the growth of pathogenic bacteria.