Influence of carbon dioxide on the activity of chicken egg white lysozyme

Rapid cooling of shell eggs by using liquid CO(2) has shown increased bactericidal effects along with saturation of the egg albumen with CO(2). Lysozyme is a bactericidal enzyme present in chicken eggs, and it lyses gram-positive bacteria. Newly laid chicken eggs have an initial pH of 7.6 to 8.5 and are saturated with CO(2). During storage, the pH gradually increases to 9.7, accompanied by a loss of CO(2). It is hypothesized that the lysozyme activity is influenced by either CO(2) concentration or pH changes resulting from CO(2) loss. The objective of this study was to determine the lytic activity of purified lysozyme and chicken egg white (unpurified lysozyme) under varying conditions of temperature, pH, and CO(2) gas concentration. Lytic activity was determined by a standard microbial assay using lyophilized Micrococcus lysodeikticus. A 2 × 4 × 2 × 2 × 3 factorial design consisting of 2 temperatures (5 and 22°C), 4 pH (4.5, 6.5, 8.0, and 9.5), 2 treatments (with and without CO(2)), 2 types of lysozyme (purified and unpurified egg white), and 3 replicates was used. The highest lytic activity was found at pH 6.5 and 22°C. At pH 4.5 and 8.0, the addition of CO(2) increased lytic activity by more than 50% at both temperatures. At pH 6.5, lytic activity was maintained with CO(2) addition at both temperatures. At pH 9.5, lytic activity without CO(2) addition was high; however, adding CO(2) reduced lytic activity to zero. In conclusion, both pH and CO(2) treatment influence lysozyme activity.