A Rapid Procedure for the Identification of Lactic Acid Bacteria Based on the Gas Chromatographic Analysis of the Cellular Fatty Acids

Abstract

This study was conducted to develop a rapid numerical procedure for the analysis of gas chromatograms of lactic acid bacteria fatty acid methylesters (FAMEs), along with an examination of some experimental conditions which affect the fatty acid composition of these bacteria. FAME determination was carried out using high resolution gas chromatography (HRGC). Although the nature and the proportion of fatty acids differed among strains, some major components, n-C14:0, n-C16:1, n-C16:0, n-C18:1, n-C18:0, and C19 cycl, were found as a group to represent more than 90% of the whole cellular fatty acids. The differences found in the relative composition of the long-chain fatty acids in paired chromatograms were used to calculate a “distance coefficient”, based on the differences found for the most important fatty acids, after their prior ranking. The procedure was initially validated with identified species, used as reference strains; then, unknown lactic acid bacteria isolates were compared to these references. The method proved to be useful for rapid comparisons between strains, provided a strict standardization occcurred prior to routine application.

Lactobacillus algidus sp. nov., a psychrophilic lactic acid bacterium isolated from vacuum-packaged refrigerated beef.

“…The presence of oleic acid as a major cellular fatty acid was considered to be distinctive of Carnobacterium and to be regarded as differential from Lactobacillus (Collins et al, 1987). However, Decallonne et al (1991) and Dykes et al (1995) showed that possession of oleic acid is not always a reliable characteristic because some Lactobacillus species also contain significant amounts of this acid.…”

Stability of cyclopropane and conjugated linoleic acids during fatty acid quantification in lactic acid bacteria

“…For many years, FA analysis has been recognized as a useful and rapid tool for the characterization of microorganisms in foods (1,2) and as a complementary analysis to taxonomic classification (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). In addition, knowledge of the FA composition may help to evaluate the nutritional quality of alternative microbiological sources of fats (9,(13)(14)(15)(16)(17).…”

“…Scheme 1 summarizes the possibilities for the analysis of fatty acids in bacteria. It shows that bacteria may be directly saponified in an acid (18) or alkaline environment (5,11,16,19,(25)(26)(27)(28)(29), or directly transesterified to fatty acid methyl esters (FAME) (30). The lipids may also be extracted and then saponified and esterified to FAME (3,6,12,13,22,24).…”

Study on Lipid Fractions of Streptococcus thermophilus by TLC, GC and GC/MS Techniques

“…Then 1% v/v of these cultures was inoculated in increasing volumes of growing medium, from 30 ml to 2 l, in order to obtain a sufficient amount of cells (about 20 g) for the fat extraction. The cells were harvested when the culture was at the stationary phase, since literature data reported that, in this period, the fatty acid composition is quite stable [2]. Cells were harvested from the medium broth and then washed twice with sterile water, by centrifugation at 8000 g x 10 min with ALC PK121 centrifuge (ALC International, Cologno Monzese, Milan, Italy).…”

“…The composition of bacteria lipids, which account for roughly 50% of cytoplasmatic membrane, has been studied due to its potential use for classification purpose [1][2][3][4][5][6]. The fatty acid composition of the whole lipid fraction, particularly in Gram-negative bacteria, has been widely investigated to support microbial characterization and to provide targets for antibacterial drugs.…”