A study into measuring the antibacterial activity of lysozyme-containing foods

Purpose - The purpose of this paper is to provide food science or biology students with a simple and reliable method of determining the antibacterial activity of a range of foods and biological materials that contain lysozyme. Design/methodology/approach - The antibacterial effects of the materials reported to contain lysozyme were assayed by gel-diffusion using the lysozyme-sensitive bacterium Micrococcus lysodeikticus. The antibacterial effects of the selected test materials, namely fresh hen egg-white, human saliva, Brussels sprouts, papaya and figs were compared against standard solutions of proprietary analytical crystalline hen egg-white lysozyme. Findings - The antibacterial activity of the test substances was similar to the effects of their lysozyme concentrations as quoted by other workers. Research limitations/implications - Antibacterial activity was higher in avian egg-white and human saliva than in the assayed plant material. Measurement of the activity in the plant material was at the limits of the sensitivity of the method. Practical implications - The two main practical methods for measuring lysozyme are either a gel-diffusion assay or a spectrophotometric procedure. Gel-diffusion assay provides a convenient procedure for student investigative work as it has a limited requirement for method development. Additionally, it is simple, cheap, reproducible and does not require specialist equipment. Further possible investigations for students are suggested. Originality/value - The paper builds on established techniques to provide a procedure that is appropriate for student use for determining lysozyme activity in a variety of biological materials.