Functional Improvement of β-Lactoglobulin by Conjugating with Alginate Lyase-Lysate

Abstract

Bovine β-lactoglobulin−alginic acid oligosaccharide (β-LG−ALGO) conjugate was prepared by the Maillard reaction to improve the function of β-LG. The molar ratio of β-LG to ALGO in the conjugates was 1:7. The isoelectric point of the conjugate was 4.55, which is lower than that of β-LG. Fluorescence studies suggested that the conformation around Trp had changed in the conjugate and that the surface of the conjugate was covered with saccharide chain. Structural analyses with monoclonal antibodies indicated that the conformation around Val15−Ile29 (β-sheet) in the conjugate had changed, while native structure was maintained around Thr125−Lys135 (α-helix). By conjugation with ALGO, β-LG was endowed with high heat stability. The emulsifying activity and the aggregating property of β-LG was improved in the conjugate. Keywords: β-Lactoglobulin; alginic acid; alginate lyase; neoglycoconjugate; functional improvement; acidic polysaccharide; protein conjugation; emulsification; solubility; retinol-binding; lipocalin