Fatty acid composition and freeze-thaw resistance in lactobacilli

The fatty acid composition and freeze-thaw resistance of eight strains of t hermophilic lactobacilli were studied. Seven of these contained the same po lar and neutral lipids, the five major components: making up 90% of the cel lular fatty acid pool being 14:0, 16:0 16:1, 18.1 and C-19 cyclopropane (cy c19:0). Strain comparison by means of cluster analysis based on the fatty a cid ratios using the overlap coefficient revealed two well defined clusters . One was formed by three strains of species Lactobacillus delbrueckii subs p. lactis and Lb. delbrueckii subsp. delbrueckii, the other included five s trains of the species Lb. delbrueckii subsp, bulgaricus, Lb. acidophilus an d Lb. helveticus. Resistance of strains with a high content of unsaturated fatty acids (66-70 %) decreased with increasing cyc19:0 concentrations. In contrast: in strains with a low concentration of unsaturated fatty acids (4 2-49 %), increasing cyc19:0 levels were associated with increased freeze-th aw resistance.