Stability of Lactic Acid Bacteria to Freezing as Related to Their Fatty Acid Composition

Abstract

The viability of Streptococcus lactis and Lactobacillus sp. A-12 after freezing at -17°C for 48 h was better preserved when the cells were grown in medium supplemented with oleic acid or Tween 80 (polyoxyethylene sorbitan monooleate). A pronounced change in the cellular fatty acid composition was noted when the bacteria were grown in the presence of Tween 80. In S. lactis the ratio of unsaturated to saturated fatty acids increased from 1.18 to 2.55 and in Lactobacillus sp. A-12 it increased from 0.85 to 1.67 when Tween 80 was added to the growth medium. The antibiotic cerulenin markedly inhibited the growth of lactic acid bacteria in tomato juice (TJ) medium but had almost no effect on the growth of the bacteria in TJ medium containing Tween 80 (or oleic acid). The antibiotic inhibited markedly the incorporation of [1- 14 C]acetate but had no inhibitory effect on the incorporation of exogenous [1- 14 C]oleate (or [1- 14 C]palmitate) into the lipid fractions of lactic acid bacteria. Thus, the fatty acid composition of lactic acid bacteria, inhibited by the antibiotic cerulenin, can be modulated by exogenously added oleic acid (or Tween 80) without the concurrent endogenous fatty acid synthesis from acetate. The data obtained suggest that cerulenin inhibits neither cyclopropane fatty acid synthesis nor elongation of fatty acid acyl intermediates. The radioactivity of cells grown in the presence of [1- 14 C]oleate and cerulenin was associated mainly with cyclopropane Δ19:0, 20:0 + 20:1, and 21:0 acids. As a consequence, cerulenin caused a decrease in the ratio of unsaturated to saturated fatty acids in lactic acid bacteria as compared with cells grown in TJ medium plus Tween 80 but without cerulenin. Cerulenin caused a decrease in the viability of S. lactis and Lactobacillus sp. A-12 after freezing at -17°C for 48 h only when Tween 80 was present in the growth medium. We conclude that the sensitivity of lactic acid bacteria to damage from freezing can be correlated with specific alterations in the cellular fatty acids.

Inactivation mechanisms of lactic acid starter cultures preserved by drying processes

“…1). An optimal cooling rate seems to be cell-type dependent and moderated by cell size, water permeability of cell membrane and the presence of a cell wall (Dumont et al 2004) as well as membrane fatty acid composition (Goldberg and Eschar 1977;Beal et al 2001). For instance, an optimal cooling rate for yeast was reported to be between 1-10°C min )1 (Mazur 1970) and at 3°C min )1 (Berny and Hennebert 1991).…”

Evidence of membrane lipid oxidation of spray-dried Lactobacillus bulgaricus during storage

“…T h e total of the areas of the chromatogram peaks of the main fatty acids was considered as the total amount of fatty acids since they represent about 82% of the total fatty acids present in Lurt. biilgurirus (Goldberg and Eschar 1977). The areas of the individual peaks were used to determine the relative percentage of each fatty acid present, and calculation of the ratio unsaturated to saturated fatty acids.…”

A low membrane lipid phase transition temperature is associated with a high cryotolerance of Lactobacillus delbrueckii subspecies bulgaricus CFL1

“…lactis and Lactobacillus spp. (Goldberg and Eschar, 1977) and Streptococcus thermophilus . The FA composition of the cellular membrane depends upon several environmental factors, including growth temperature, pH, culture medium, and composition, among others.…”