Effect of lysozyme or nisin on survival of some bacteria treated with high pressure at subzero temperature

Abstract

The aim of this work was to examine the inactivation of some Gram-positive and Gram-negative bacteria exposed to the pressure of 193 MPa at –20 °C in the presence of lysozyme or nisin at concentration of 400 µg/ml. The highest effect of pressure at subzero temperature and lysozyme was found with pressure sensitive Pseudomonas fluorescens; viable cells of this strain were not detected in 1 ml of sample after combined treatment. The action of pressure at subzero temperature and lysozyme or nisin against Escherichia coli led to synergistic reduction by 0.7 or 1.6 log cycles, respectively, while it was practically insignificant for two Staphylococcus aureus strains. Viability loss of E. coli and S. aureus occurred during storage for 20 h of the samples at 37 and 5 °C, which were previously pressurized with lysozyme or nisin. The synergistic effect of pressure and nisin at pH 5 against E. coli cells just after the pressure treatment was lower than that at pH 7, however, the extent of the lethal effect after storage was higher.

Cecropin A Improves the Antibacterial Activity of Hen Egg White Lysozyme against Challenging Salmonella enterica Serovars

“…Bacterial growth phase has a significant impact on the overall antibacterial activity of the applied PGH. In the logarithmic growth phase, bacteria are more sensitive, whereas the stationary grown phenotypes are found to be more refractory [ 23 , 42 , 43 , 44 ]. In the current study, we evaluated the antibacterial outcome of combining HEWL with ascending concentrations of CecA against bacteria in both stationary and logarithmic growth phases.…”

Effects of Pressurization on Some Contamination Flora in Beef Pate

“…Some of them only determined the amount of injured cells by taking the difference between the counts of only the living cells followed by the elimination of the injured ones by the selective agent like NaCl in selective agar and the counts of all cells including both injured and living ones by the nonselective agar namely Tryptose Soy Agar or Sorbitol MacConkey Agar (Bozoglu and others 2004; Somolinos and others 2008). Some studies did not make any enrichment and instead, preferred to count directly only the viable cells without any enrichment (Kumar and others 2009; Malinowska‐Panczyk and Kolodziejska 2009; Han and others 2010) by disregarding the possibility of the injured cell existence due to pressure. Finally, some studies like this study, made enrichment before the main enumeration to give a chance to the injured cells to recover their wounds caused by the pressure (Oblinger and Kraft 1973; Wuytack and others 2002; Lee and others 2012).…”