Conjugation of Lysozyme and Epigallocatechin Gallate for Improving Antibacterial and Antioxidant Properties

One of the main interests in the food industry is the preservation of food from spoilage by microorganisms or lipid oxidation. A novel alternative is the development of additives of natural origin with dual activity. In the present study, a chemically modified lysozyme (Lys) with epigallocatechin gallate (EGCG) was developed to obtain a conjugate (Lys-EGCG) with antibacterial/antioxidant activity to improve its properties and increase its application potential. The modification reaction was carried out using a free radical grafting method for the Lys modification reaction, using ascorbic acid and hydrogen peroxide as radical initiators in an aqueous medium. The synthesis of Lys-EGCG conjugate was confirmed by spectroscopic (FT-IR, ¹H-RMN, and XPS) and calorimetry differential scanning (DSC) analyses. The EGCG binding to the Lys biomolecule was quantified by the Folin-Ciocalteu method; the antibacterial activity was evaluated by minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MCB) against Staphylococcus aureus and Pseudomonas fluorescens; the antioxidant activity was evaluated by ABTS, DPPH, and FRAP. The spectroscopic results showed that the Lys-EGCG conjugate was successfully obtained, and the DSC analysis revealed a 20 °C increase (P < 0.05) in the denaturation temperature of Lys due to EGCG modification. The EGCG concentration in Lys-EGCG was 97.97 ± 4.7 µmol of EGCG/g of sample. The antibacterial and antioxidant activity of the Lys-EGCG conjugate was higher (P < 0.05) than pure EGCG and Lys. The chemical modification of Lys with EGCG allows for the bioconjugate with a dual function (antibacterial/antioxidant), broadening the range of Lys and EGCG applications to different areas such as food, cosmetic, and pharmaceutical industries.