Novel Antifungal Compounds, Spermine-Like and Short Cyclic Polylactates, Produced by Lactobacillus harbinensis K.V9.3.1Np in Yogurt.

Amor Mosbah,Gwenaelle Le Blay,Nicolas Le Yondre,Mouna Mahjoubi,Philippe Jéhan,Emilie Delavenne,Michèle Baudy-Floc’H,Ameur Cherif,Yasmine Souissi,Jérôme Mounier,Arnaud Bondon

doi:10.3389/fmicb.2018.02252

Abstract

Lactobacillus harbinensis K.V9.3.1Np was described as endowed with high antifungal activity. Most of the studies associated this activity to the produced organic acids, i.e., lactic acid, acetic acid, and hexanoic acid. The aim of this study was to purify and identify, other not yet described, antifungal molecules produced by L. harbinensis K.V9.3.1Np when used in yogurt fermentation. Active compounds were extracted through several extraction processes using organic solvents and protein precipitation. The fractions of interest were purified using flash chromatography and preparative HPLC for specific characterization. The bioactive compounds identification was performed using Nuclear Magnetic Resonance and Mass Spectrometry. Activity tests against Penicillium expansum and Yarrowia lipolytica showed that the active compounds from L. harbinensis K.V9.3.1Np are benzoic acid and a polyamine identified as a spermine analog, which has not been reported earlier. However, the highest activity was shown by a mixture of short (n = 2–5) polycyclic lactates. Our overall results demonstrate the efficiency of the proposed extraction/purification approach. The new compounds described here have promising antifungal activities but further studies are still needed to decipher their mode of action and production pathways. Even though, they present an interesting potential application in food, feed, as well as, in pharmaceutical industries and could serve as alternative to chemical additives.

Highlights

There is a growing concern on microbiological safety of dairy food as their contamination can cause considerable economic losses
In the current work, using an untargeted approach, we focused on the identification, purification, and characterization of all non-acids antifungal compounds produced by L. harbinensis
After the fermentation process with L. bulgaricus, S. thermophilus amended or not with L. harbinensis K.V9.3.1Np, the yogurt culture supernatant was separated into different fractions using ammonium sulfate precipitation, ethyl acetate, and dichloromethane

Summary

Introduction

There is a growing concern on microbiological safety of dairy food as their contamination can cause considerable economic losses. Identification of New Antifungal Compounds From Lactobacillus harbinensis factors promoting fungal growth and metabolite secretion. Fungal growth induces a decrease in the acidity promoting subsequently the growth of some undesirable microorganisms (Leyva Salas et al, 2017). The need of preventing food from microbiological spoilage challenged scientists to develop appropriate preservative solutions. Avoiding microbial contamination is achieved through suitable treatment, and/or appropriate preservative agents or by preventing the growth and the activity of those that were not eliminated after treatment (Leyva Salas et al, 2017)

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