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Influence of cooling temperature and duration on cold adaptation of Lactobacillus acidophilus RD758.

Wang Y, Delettre J, Guillot A, Corrieu G, Béal C

UMR Génie et Microbiologie des Procédés Alimentaires, INA P-G, INRA, 78850 Thiverval-Grignon, France.

The effect of different cooling temperatures and durations on resistance to freezing and to frozen storage at -20 degrees C in Lactobacillus acidophilus RD758 was studied, by using a central composite rotatable design. A cold adaptation was observed when the cells were maintained at moderate temperature (26 degrees C) for a long time (8h) before being cooled to the final temperature of 15 degrees C. These conditions led to a low rate of loss in acidification activity during frozen storage (0.64 minday(-1)) and a high residual acidification activity after 180 days of frozen storage (1011 min). The experimental design allowed us to determine optimal cooling conditions, which were established at 28 degrees C during 8h. Adaptation to cold temperatures was related to an increase in the unsaturated to saturated fatty acid ratio and in the relative cycC19:0 fatty acid concentration. Moreover, an increased synthesis of four specific proteins was observed as an adaptive response to the optimal cooling conditions. They included the stress protein ATP-dependent ClpP and two cold induced proteins: pyruvate kinase and a putative glycoprotein endopeptidase.

Published 31 May 2005 in Cryobiology, 50(3): 294-307.
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