Functional Improvements to β-Lactoglobulin by Preparing an Edible Conjugate with Cationic Saccharide Using Microbial Mransglutaminase (MTGase)

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Bovine β-lactoglobulin (BLG) was conjugated with cationic saccharides to improve its functions. We used a polylysine-dextran conjugate (PL-Dex) as the cationic saccharide which had been prepared by the Maillard reaction. The molar ratio of PL:Dex was 1:1. The emulsifying property of PL in the acidic pH range was improved by conjugating with Dex. BLG and PL-Dex were conjugated by using microbial transglutaminase (MTGase), the effective conjugation being confirmed by SDS–PAGE. The molar ratio of BLG:PL-Dex was 1:1. Structural analyses by a fluorescence study, ELISA with monoclonal antibodies and measurement of the retinol-binding activity indicated that the conjugates had almost retained the native structure of BLG. The emulsifying property of BLG in the acidic pH range and in the presence of NaCl was improved by conjugating with PL-Dex. The immunogenicity of BLG was reduced by this conjugation, while the antigenicity of the BLG-PL-Dex conjugate was similar to that of BLG in BALB/c mice.