Title
Heat stress adaption of Escherichia coli under dynamic conditions: effect of inoculum sizeHeat stress adaption of Escherichia coli under dynamic conditions: effect of inoculum size
Author
Faculty/Department
Faculty of Applied Engineering Sciences
Publication type
article
Publication
Oxford,
Subject
Chemistry
Engineering sciences. Technology
Source (journal)
Letters in applied microbiology. - Oxford
Volume/pages
51(2010):4, p. 450-455
ISSN
0266-8254
ISI
000281829100014
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Abstract
Aims: When subjected to dynamic temperatures surpassing the expected maximum growth temperature, Escherichia coli K12 MG1655 shows disturbed growth curves. These irregular population dynamics were explained by considering two subpopulations, i.e. a thermoresistant and a thermosensitive one (Van Derlinden et al. 2010a). In this paper, the influence of the initial cell concentration on the subpopulations' dynamics is evaluated. Methods and Results: Experiments were performed in a bioreactor with the temperature increasing from 42 to 65 center dot 2 degrees C (1 and 4 degrees C h-1) with varying initial cell concentrations [6, 12 and 18 ln(CFU ml-1)]. When started from the highest cell concentration, the population was characterized by a higher overall maximum growth temperature and a higher inactivation temperature. For all experimental set-ups, resistant cells were still growing at the final temperature of 65 center dot 2 degrees C. Conclusions: The initial cell concentration had no effect on temperature resistance. The increase in temperature resistance of the sensitive subpopulation was because of the change of the physiological state to the stationary phase. Significance and Impact of the Study: A higher initial cell concentration leads to higher heat stress adaptation when cultures reach a maximum cell concentration. The observed growth at a temperature of 65 center dot 2 degrees C is very important for food safety and the temperature treatment of micro-organisms.
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