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Applied and Environmental Microbiology, September 1999, p. 4148-4154, Vol. 65, No. 9
Microbiology & Preservation, Unilever
Research Vlaardingen, Vlaardingen, The Netherlands
Received 25 March 1999/Accepted 30 June 1999
Nisin in combination with ultrahigh-pressure treatment (UHP) showed
strong synergistic effects against Lactobacillus plantarum and Escherichia coli at reduced temperatures (<15°C).
The strongest inactivation effects were observed when nisin was present
during pressure treatment and in the recovery medium. Elimination
(>6-log reductions) of L. plantarum was achieved at 10°C
with synergistic combinations of 0.5 µg of nisin per ml at 150 MPa
and 0.1 µg of nisin per ml at 200 MPa for 10 min. Additive effects of
nisin and UHP accounted for only 1.2- and 3.7-log reductions,
respectively. Elimination was also achieved for E. coli at
10°C with nisin present at 2 µg/ml, and 10 min of pressure at 200 MPa, whereas the additive effect accounted for only 2.6-log reductions.
Slight effects were observed even against the yeast Saccharomyces
cerevisiae with nisin present at 5 µg/ml and with 200 MPa of
pressure. Combining nisin, UHP, and lowered temperature may allow
considerable reduction in time and/or pressure of UHP treatments. Kill
can be complete without the frequently encountered survival tails in
UHP processing. The slightly enhanced synergistic kill with UHP at
reduced temperatures was also observed for other antimicrobials, the
synthetic peptides MB21 and histatin 5. The postulated mode of action
was that the reduced temperature and the binding of peptides to the
membrane increased the efficacy of UHP treatment. The increases in
fatty acid saturation or diphosphatidylglycerol content and the
lysylphosphatidyl content of the cytoplasm membrane of L. plantarum were correlated with increased susceptibility to UHP
and nisin, respectively.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Synergistic Actions of Nisin, Sublethal Ultrahigh
Pressure, and Reduced Temperature on Bacteria and Yeast
*
Corresponding author. Mailing address: Microbiology & Preservation, Unilever Research Vlaardingen, P.O. Box 114, 3130 AC
Vlaardingen, The Netherlands. Phone: 31-10-4605832. Fax: 31-10-4605188. E-mail: Pieter-ter.Steeg{at}Unilever.com.
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