Aims: The aim of this study was to isolate and identify bacteriocin-producing lactic acid bacteria (LAB) issued from Mongolian airag (traditional fermented mare's milk), and to purify and characterize bacteriocins produced by these LAB. Methods and Results: Identification of the bacteria (Enterococcus durans) was carried out on the basis of its morphological, biochemical characteristics and carbohydrate fermentation profile and by API50CH kit and 16S rDNA analyses. The pH-neutral cell-free supernatant of this bacterium inhibited the growth of several Lactobacillus spp. and food-borne pathogens including Escherichia coli, Staphylococcus aureus and Listeria innocua. The antimicrobial agent (enterocin A5-11) was heat stable and was not sensitive to acid and alkaline conditions (pH 2-10), but was sensitive to several proteolytic enzymes. Its inhibitory activity was completely eliminated after treatment with proteinase K and a-chymotrypsin. The activity was however not completely inactivated by other proteases including trypsin and pepsin. Three-step purification procedure with high recovery yields was developed to separate two bacteriocins. The applied procedure allowed the recovery of 16% and 64% of enterocins A5-11A and A5-11B, respectively, present in the culture supernatant with purity higher than 99%. SDS-PAGE analyses revealed that enterocin A5-11 has a molecular mass of 5000 Da and mass spectrometry analyses demonstrates molecular masses of 5206 and 5218 Da for fractions A and B, respectively. Amino acid analyses of both enterocins indicated significant quantitative difference in their contents in threonine, alanine, isoleucine and leucine. Their N-termini were blocked hampering straightforward Edman degradation. Conclusions: Bacteriocins A5-11A and B from Ent. durans belong to the class II of bacteriocins. Significance and Impact of the Study: Judging from molecular masses, amino acid composition and spectrum of activities, bacteriocins A5-11A and B from Ent. durans show high degree of similarity with enterocins L50A and L50B isolated from Enterococcus faecium (Cintas et al. 1998(Cintas et al. , 2000 and with enterocin I produced by Ent. faecium 6T1a, a strain originally isolated from a Spanish-style green olive fermentation (Floriano et al. 1998).

Cuticle function is closely related to the structure of the cutin polymer. However, the structure and formation of this hydrophobic polyester of glycerol and hydroxy/epoxy fatty acids has not been fully resolved. An apoplastic GDSL-lipase known as CUTIN SYNTHASE1 (CUS1) is required for cutin deposition in tomato (Solanum lycopersicum) fruit exocarp. In vitro, CUS1 catalyzes the self-transesterification of 2-monoacylglycerol of 9(10),16-dihydroxyhexadecanoic acid, the major tomato cutin monomer. This reaction releases glycerol and leads to the formation of oligomers with the secondary hydroxyl group remaining nonesterified. To check this mechanism in planta, a benzyl etherification of nonesterified hydroxyl groups of glycerol and hydroxy fatty acids was performed within cutin. Remarkably, in addition to a significant decrease in cutin deposition, mid-chain hydroxyl esterification of the dihydroxyhexadecanoic acid was affected in tomato RNA interference and ethyl methanesulfonate-cus1 mutants. Furthermore, in these mutants, the esterification of both sn-1,3 and sn-2 positions of glycerol was impacted, and their cutin contained a higher molar glycerol-to-dihydroxyhexadecanoic acid ratio. Therefore, in planta, CUS1 can catalyze the esterification of both primary and secondary alcohol groups of cutin monomers, and another enzymatic or nonenzymatic mechanism of polymerization may coexist with CUS1-catalyzed polymerization. This mechanism is poorly efficient with secondary alcohol groups and produces polyesters with lower molecular size. Confocal Raman imaging of benzyl etherified cutins showed that the polymerization is heterogenous at the fruit surface. Finally, by comparing tomato mutants either affected or not in cutin polymerization, we concluded that the level of cutin cross-linking had no significant impact on water permeance.Cuticles are ubiquitous hydrophobic barriers at the surfaces of aerial plant organs. These complex hydrophobic assemblies consist of a biopolymer, cutin, coated and filled with waxes and can also comprise embedded cell wall polysaccharides. Waxes comprise solventsoluble aliphatic molecules with long hydrocarbon chains, terpenes, and steroids (Kunst and Samuels,

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Glycation by the Maillard reaction is an ubiquitous reaction of condensation of a reducing sugar with amino groups of proteins, which products could improve the functional and/or biological properties for food and non-food uses. It can induce structural modifications in proteins, modifying their properties. The aim of this work was to investigate the association behavior and the conformational changes of beta-lactoglobulin (BLG) after its glycation by the Maillard reaction with several alimentary sugars (arabinose, galactose, glucose, lactose, rhamnose and ribose). Protein samples were heated in the presence or in the absence (heated control) of different sugars during 3 days at 60 degrees C. Glycation induced oligomerization of BLG monomers. Depending on the reactivity of the sugar, the population of produced oligomers showed smaller or greater heterogeneity in molecular masses. Analysis of modified BLG by circular dichroism and by its susceptibility to pepsinolysis showed that the conditions of heating used did not significantly alter the conformation of BLG. Heating of BLG in presence of sugars induced only minor structural modification, when using the less reactive sugars such as lactose and rhamnose. It was, however, at the origin of major three-dimensional destructuring in the case of the more reactive sugars such as arabinose and ribose. Pepsinolysis of glycated BLG did not affect about 62 and 35% of the protein molecules modified with lactose or rhamnose, and arabinose or ribose, respectively. The increase of susceptibility of glycated BLG to pepsinolysis could be related to the alteration of the conformation of the protein when glycation was performed with highly reactive sugars, as observed by circular dichroism and calorimetry analysis.

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