Recombinant pediocin in Lactococcus lactis:increased production by propeptide fusion and improved potency by co-production with PedC

We describe the impact of two propeptides and PedC on the production yield and the potency of recombinant pediocins produced in Lactococcus lactis. On the one hand, the sequences encoding the propeptides SD or LEISSTCDA were inserted between the sequence encoding the signal peptide of Usp45 and the structural gene of the mature pediocin PA-1. On the other hand, the putative thiol-disulfide oxidoreductase PedC was coexpressed with pediocin. The concentration of recombinant pediocins produced in supernatants was determined by enzyme-linked immunosorbent assay. The potency of recombinant pediocins was investigated by measuring the minimal inhibitory concentration by agar well diffusion assay. The results show that propeptides SD or LEISSTCDA lead to an improved secretion of recombinant pediocins with apparently no effect on the antibacterial potency and that PedC increases the potency of recombinant pediocin. To our knowledge, this study reveals for the first time that pediocin tolerates fusions at the N-terminal end. Furthermore, it reveals that only expressing the pediocin structural gene in a heterologous host is not sufficient to get an optimal potency and requires the accessory protein PedC. In addition, it can be speculated that PedC catalyses the correct formation of disulfide bonds in pediocin.</p

Dynamics and acidification properties of raw milk bacterial communities during serial fermentations

International audienc

A MALDI-TOF based study of the in-vivo assembly of glutenin polymers of durum wheat

Wheat grain is recognized as the most suitable raw material for bread and pasta making due to the unique viscoelasticity of its storage proteins, and in particular its glutenin polymers. During grain development, low molecular weight (LMW) and high molecular weight (HMW) glutenin subunits (GS) gradually assembled through inter-chain disulfide bonds. Despite the impact of the final glutenin polymer size distribution on wheat technological quality, little is known concerning the oxidative folding of GS. In particular, which of their cysteine (Cys) residues participate to GS inter-chains remains putative. In this study GS from immature Triticum durum wheat grain were separated (10 SDS-PAGE) and digested into peptides, which were analyzed by MALDI-TOF/TOF. Differential alkylation of free and disulfide bonded Cys allowed us to identify the oxidative folding state of five types of LMW-GS and of the 1Bx20 HMW-GS. GS as monomers or as part of small oligomers carried a high number of free cysteine residues. In addition, some Cys residues, hitherto assumed as involved in intra-chain disulfide bonds, appeared simultaneously in free and oxidized forms. The last result could be assigned to their partial-blocking by glutathione. We concluded that the complete oxidative folding of LMW-GS is a late event, subsequent to GS inter-chain pairing. (C) 2014 Elsevier Ltd. All rights reserved

Dynamique et propriétés d’acidification de communautés bactériennes du lait cru lors de fermentations séquentielles

International audienc

Dynamique et propriétés d’acidification de communautés bactériennes du lait cru lors de fermentations séquentielles

International audienc

Dynamics and acidification properties of raw milk bacterial communities during serial fermentations

International audienc

Physicochemical control of durum wheat grain filling and glutenin polymer assembly under different temperature regimes

Durum wheat is grown in the Mediterranean area where drought and high temperature frequently prevail and impact grain texture, composition and yield. The purpose of this work was to examine the effect of high temperature on grain development and final composition according to the timing of exposure. High temperature (up to 27.5 degrees C) was applied either during the linear grain filling or drying phases or during whole grain development. The dynamics of grain dry mass, water, glutenin polymers, and protein bodies during grain development were determined. Irrespective of high temperature timing, the arrest of grain filling was observed at 45.9% grain moisture content. At that point, starch granules included in endosperm cells reached their physical packing limit, limiting further deposits. HT applied before physiological maturity shortened the duration of grain filling and resulted in a significant increase in grain protein concentration and in the proportion of vitreous grain. Late formation of sodium dodecyl sulfate (SDS)-insoluble glutenin polymers below 32% grain moisture content was also favored. The ability of wheat storage protein to form a viscoelastic matrix embedding starch granules at the beginning of grain desiccation is proposed to be mandatory for gaining vitreous grains and a high proportion of SDS-insoluble glutenin polymers. (c) 2011 Elsevier Ltd. All rights reserved

Microbiome engineering for biopreservation of food

International audienc

Microbiome engineering as a biopreservation approach to reduce Listeria monocytogenes in food

International audienc

Oxidative stability of DHA phenolic ester

International audienceDocosahexaenoic acid vanillyl ester (DHA-VE) was synthesized from docosahexaenoic acid ethyl ester (DHA-EE) and vanillyl alcohol by a solvent-free alcoholysis process catalysed by Candida antarctica lipase B. Oxidative stability of pure DHA-VE and the crude reaction medium consisting of 45% DHA-VE and 55% DHA-EE were compared with that of DHA-EE under various storage conditions. Oxidation progress was followed by determination of conjugated dienes and FTIR measurements. Analyses showed that DHA-EE was rapidly oxidised under all storage conditions in comparison with DHA-VE and crude reaction medium, whatever the temperature and the storage time. The grafting of vanillyl alcohol appeared as a powerful way to stabilize DHA against oxidation. Thanks to their stability, both DHA-VE and the crude reaction medium, allowing the production of the ester, offer huge potential as functional ingredients