Oxylipins biosynthesis in Lactobacillus helveticus in the presence of oxidative stress

Montanari, Chiara (2011) Oxylipins biosynthesis in Lactobacillus helveticus in the presence of oxidative stress, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Scienze e biotecnologie degli alimenti, 23 Ciclo.
Documenti full-text disponibili:
[img] Documento PDF (English) - Accesso riservato - Richiede un lettore di PDF come Xpdf o Adobe Acrobat Reader
Download (3MB)


This PhD thesis is aimed at studying the possible pathways and the mechanisms that can trigger oxylipins biosynthesis, and particularly that of short chain aldehydes and alcohols, in Lactobacillus helveticus, also in the presence of oxidative stress, using a totally labelled linoleic acid as precursor. In plants and fungi these molecules, involved in defence mechanisms against pathogens and in communication systems, derive from the oxidation of cellular unsaturated fatty acids (UFAs) and their accumulation is associated with stress exposure. Since some oxylipins are produced also by lactobacilli, it is possible to hypothesize that a metabolic pathway from UFAs to oxylipins, similar to what happens in plants and fungi, is present also in lactic acid bacteria. The results obtained pointed out that some volatile molecules are the result of UFAs catabolism, since they appear only when cells are incubated in their presence. Labelled linoleic acid is integrated in the membrane and subsequently transformed into aldehydes and alcohols, whose extent and carbon atoms number depend on stress exposure. The enzymes responsible for this metabolic pathway in plants and fungi (e.g. lipoxygenase, dioxygenase) seem to be absent in Lactobacillus helveticus and in other lactobacilli. Proteomic analyses show the over expression of many proteins, including thioredoxin reductase (part of the bacterial oxidative defence system), mainly in cells grown with linoleic acid without oxidative stress exposure, confirming that linoleic acid itself induces oxidative stress. 6 general oxidoreductases (class including dioxygenases and peroxidase) were found and therefore a deeper investigation on them could be productive in elucidating all steps involved in oxylipins biosynthesis in bacteria. Due to the multiple role of oxylipins (flavouring agents, antimicrobial compounds and interspecific signalling molecules) the identification of genes involved and regulating factors should have an important biotechnological impact, also allowing the overproduction of selected bioactive molecules.

Tipologia del documento
Tesi di dottorato
Montanari, Chiara
Dottorato di ricerca
Scuola di dottorato
Scienze agrarie
Settore disciplinare
Settore concorsuale
Data di discussione
27 Maggio 2011

Altri metadati

Gestione del documento: Visualizza la tesi