Cryotolerance and cold stress in lactic acid bacteria

The necessity for better control of lactic acid bacteria (LAB) which are widely used in food biotechnology, requires an increase in our knowledge concerning the behaviour at low temperature of these organisms (starter freezing, ripening at positive low temperature, food storage). Study of the cold stress responses in LAB needs to consider: (i) positive and negative low temperatures, (ii) the duration of the exposure to low temperature leading to a "shock" or an "acclimation", (iii) microorganism grouping according to their cardinal growth temperatures. Furthermore, the connection between the stress generated by transfer of LAB to a low temperature environment and the correlated response, may be analysed by three approaches: (i) the physiological response of the cell (growth and cryotolerance), (ii) the generated biochemical modifications (degree of fatty acid desaturation and protein profile), (iii) the control of the response. Recent results in molecular genetics concerning the cold stress responses in LAB seems to be insufficiently correlated to current understanding of biochemical and physiological behaviours, such as cryotolerance.