DEGRADATION OF CAPRINE CASEIN BY PAPAIN, AND ITS ANTIBACTERIAL EFFECT TOWARDS ESCHERICHIA COLI

Abstract

Caprine milk is one of the animal protein sources with high nutrition and relatively easy to digest. Caprine milk has high protein content (3.4 %) which is potential to produce bioactive peptides such as antimicrobial peptides. This study was to analyze the profile of peptides from caprine casein hydrolyzed with papain and analyze their bioactivity as antibacterial toward food pathogens Escherichia coli and Staphylococcus aureus. The caprine casein was separated by adding HCl to the defatted caprine milk until the pH reached isoelectric point. The coagulated protein was recovered by centrifugation. α-Casein (MW 32 kDa), β-casein (MW 24 kDa) and other caprine protein were hydrolyzed using papain enzyme (4000-6000 units∙g-1) for 15 minutes leaving κ-casein (MW 21 kDa) and producing one new peptide band (MW 10 kDa) as seen following SDS-PAGE. Both casein and peptide hydrolysates inhibited Escherichia coli but not Staphylococcus aureus. Further analysis showed that unhydrolyzed casein reduced Escherichia coli growth significantly by 1.6 log after 2 hours of exposure and the inhibition was increased by exposure time. However, the hydrolyzed casein only shows little (non-significant) inhibition after 4 hours incubation with the bacteria.

Keywords

• antibacterial
• caprine casein
• casein hydrolysates
• escherichia coli
• papain