# Chromatographic and Molecular Insights into Fatty Acid Profiles of Thermophilic Lactobacillus Strains: Influence of Tween 80TM Supplementation

## TL;DR

This study examines how Tween 80TM affects fatty acid profiles in thermophilic Lactobacillus strains using advanced analytical methods.

## Contribution

The study provides detailed molecular insights into fatty acid profiles and highlights the role of Tween 80TM in differentiating lactobacilli strains.

## Key findings

- Six saturated fatty acids and various branched, hydroxy, and unsaturated fatty acids were identified.
- Significant differences were observed in the identification of specific fatty acids like C18:1,cis-9 and cycC19:0,cis-10,11.
- The absence of Tween 80TM in MRS medium helped differentiate lactobacilli based on growth patterns.

## Abstract

The molecular fatty acid (FA) profiles of seven certified thermophilic Lactobacillus strains, including the influence of an extracellular source of oleic acid (as Tween 80TM), were characterised using advanced chromatographic and spectrometric methods. Cyclic and conjugated fatty acids were identified by GC-MS using co-injections with authentic standards, ECL, and diagnostic EI ions, with a secondary confirmation using literature data. Additionally, the molecular-level characterisation of fatty acid profiles of bacterial cells was summarised using the latest analytical approaches, highlighting inconsistencies and differences reported in previous studies. Six saturated fatty acids, two single-branched fatty acids with iso and anteiso structures, one hydroxy fatty acid, nine unsaturated fatty acids with one double bond, two fatty acids with unsaturated double bonds, six fatty acids with conjugated bonds, and three fatty acids with a cyclic part in the carbon chain were identified. Within these fatty acids, we also demonstrated the limitations of molecular chromatographic resolution and structural discrimination, which impacted the effective identification of fatty acids in our research. We confirmed the significant differences in terms of the identification of C18:1,cis-9 and C18:1,cis-11 acids, as well as cycC19:0,cis-10,11, and cycC19:0,cis-9,10 acids. The observations at the molecular–physiological interface related to the lack of growth of L. acidophilus strains and the visibly reduced growth of L. delbrueckii subsp. lactis ATCC 4797 in the MRS without the addition of Tween 80TM allowed us to confirm that the exclusion of this medium is useful in differentiating the lactobacilli.