99D-25 |
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L. M. MICHAEL1, S. Zivanovic2, and D. A. Golden1. (1) Department of Food Science and Technology, University of Tennessee, 2605 River Drive, Knoxville, TN 37996-4591, (2) Dept. of Food Science & Technology, Univ. of Tennessee, Food Chemistry & Biophysics Labs., 2605 River Dr., Knoxville, TN 37996-4591 Determination of surface charge of microbial cells and biopolymers is of paramount importance for understanding and modeling their behavior and function in various conditions. The overall goal of our research is to examine correlations between microbial surface charge and susceptibility to antimicrobial biopolymers. Specific objectives of this study were to determine surface charge of Saccharomyces cerevisiae cells as affected by environmental pH and culture age, and to determine the surface charge of protein (bovine serum albumin, BSA) in broad pH range. Surface charge of microbial cells and biopolymers was measured at 25°C using Zeta PALS. BSA was dissolved in 1mM KCl and pH of the solution was adjusted from 2 to 11. S.cerevisiae was used as a test microorganism. The yeast was cultured in YM broth at 25°C with constant shaking. The surface charge, measured as zeta potential, was determined in log phase, at the beginning of stationary phase, and during stationary phase. The effect of pH on the charge of yeast cells was evaluated at pH 4, 5.5, and 7 after 24 hr incubation at 25°C. Our results showed that as pH increases, BSA becomes more negatively charged. Zeta potential changed from -32.9mV at pH=11.0 to 36.0mV at pH=2.4, and isoelectic point was determined to be pH=4.6. The surface charge of S.cerevisiae cells did not significantly change from log to stationary phase but was affected by environmental pH. The zeta potential was –23.3mV and -21.1mV after 12 and 24hr incubation at 25°C at pH=7, respectively. These data significantly contribute to our understanding of how culture age and environmental conditions can affect the cellular response to antimicrobial agents. Furthermore, understanding the changes of surface charge of biopolymers at different pH helps when explaining their interactions and functional properties, such as solubility, gelling, and film-formation.
Session 99D, Food Microbiology: General
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