The existing literature on the role of fatty acids in microbial temperature adaptation is reviewed. Several modes of change of cellular fatty acids at varying environmental temperatures are shown to exist in yeasts and fungi, Gram-negative bacteria, and bacteria containing iso- and anteiso-branched fatty acids, as well as in a few Gram-positive bacteria. Consequently, the degree of fatty acid unsaturation and cyclization, fatty acid chain length, branching, and cellular fatty acid content increase, decrease, or remain unaltered on lowering the temperature. Moreover, microorganisms seem to be able to change from one mode or alter the cellular fatty acid profile temperature dependently to another on lowering the temperature, as well as even within the same growth temperature range, depending on growth conditions. Therefore, the effect of the temperature on cellular fatty acids appears to be more complicated than known earlier. However, similarities found in the modes of change of cellular fatty acids at varying environmental temperatures in several microorganisms within the above mentioned groups support the existence of a limited amount of common regulatory mechanisms. The models presented enable the prediction of temperature-induced changes occurring in the fatty acids of microorganisms, and enzymatic steps of the fatty acid biosynthesis that possibly are under temperature control.

The interchange of octadecenoic acids and dihydrosterulic acid was a response of aerobically growing LactobaciZZus fermenturn to changes in growth temperature. Oleic and vaccenic acid contents decreased both at temperatures below 20 "C and above 26 "C, showing mirror image behaviour, with a concomitant increase in dihydrostemlic acid. A temperature-dependent shift from vaccenic to oleic acid synthesis, and the conversion of the latter to dihydrosterulic acid was responsible for the overall change. Consequently, the degree of fatty acid unsaturation decreased at temperatures above 26 "C, whereas the degree of cyclization increased. The converse occurred below 20 "C. The relative amount of lactobacillic acid, total cellular fatty acid content, and mean fatty acid chain length were practically temperature-independent. The occurrence of oleic acid is thought to be related to aerobic growth conditions.

Cellular fatty acids of 10 strains of lactic acid bacteria were analyzed. The purpose of this work was to find lactic acid bacteria with high lactobacillic acid contents. The bacteria studied were unable to synthesize oleic acid. Some strains did not synthesize lactobacillic acid, although all were able to form dihydrosterculic acid. Twenty-one to thirty-four percent of the fatty acid content of Lactobacillus fermentum and L. buchneri was lactobacillic acid, and these species were chosen for future studies of environmental factors affecting cyclopropane fatty acid synthesis.

A method for the production of conjugated linoleic acid (CLA) from linoleic acid (LA) using growing cultures of Propionibacterium freudenreichii ssp. shermanii JS was developed. The growth inhibitory effect of LA was eliminated by dispersing it in a sufficient concentration of polyoxyethylene sorbitan monooleate detergent. For the whey permeate medium used, the optimum LA:detergent ratio was 1:15 (w/w). As a result, the cultures tolerated at least 1000 microg x mL(-1) LA, which was converted to CLA with 57%-87% efficiency. The cis-9, trans-11 and trans-9, cis-11 isomers constituted 85%-90% of the CLA produced. The feasibility of the method was demonstrated also in de Man Rogosa-Sharpe (MRS) broth.