Formation of dihydrophenolic acids and aroma-active volatile phenols by new strains of Limosilactobacillus fermentum

Previously undescribed species of Limosilactobacillus fermentum isolated from wholemeal buckwheat sourdough were identified by MALDI-TOF/MS and 16S rRNA analysis. The metabolism of 6 hydroxycinnamic acids by L. fermentum 6P1, 6P2 and 7P2 strains provided mostly o-, m-, p-dihydrocoumaric, dihydroferulic, dihydrocaffeic and dihydrosinapic acids. The ratio of hydroxyphenylpropionic acids to 4-vinylphenols was strain-to-strain specific. Decarboxylation of free cinnamic acid to potentially toxic styrene was low (1.8-23.9 mol. %) in all Limosilactobacillus strains tested. At a concentration of 13.6 mmol/L, reduced p-dihydrocoumaric and dihydroferulic acids were shown to cause less growth inhibition than their precursors, while specific growth rates mu increased significantly. L. fermentum POH with the highest sensitivity to phenolic acids exhibited the lowest ability to reduce hydroxycinnamic acids (11.8-44.5%) by phenolic acid reductase. Metabolomic experiments with chemically labelled D-glucose-d(12) provided a deeper insight into electron transfer to polyphenols as the final acceptor. To the best of our knowledge, deuterium transfer to dideuteroferulic acid was observed for the first time.

Automated summary

A previously undescribed species of Limosilactobacillus fermentum isolated from wholemeal buckwheat sourdough was identified and its metabolism of 6 hydroxycinnamic acids was studied. The study found that the decarboxylation of free cinnamic acid to potentially toxic styrene was low in all strains tested. Additionally, it was discovered that reduced p-dihydrocoumaric and dihydroferulic acids caused less growth inhibition than their precursors.