Microbial Dynamics during labneh Ambaris Production in Earthenware Jars

The responses of various microbial populations to modifications in the physicochemical properties of a food matrix, as well as interactions between these populations already present, are the main factors that shape microbial dynamics in that matrix. This work focused on the study of microbial dynamics during labneh Ambaris production, a traditional Lebanese concentrated fermented goat milk made in jars during 3 months. This was assessed in two earthenware jars at a production facility. DNA metabarcoding of the ITS2 region as well as the V3-V4 region of the 16S rRNA gene was used to characterize the fungal and bacterial communities, respectively. Viable bacterial isolates were also identified by Sanger sequencing of the V1-V4 region of the 16S rRNA gene. Our results showed that the dominant microorganisms identified within labneh Ambaris (Lactobacillus kefiranofaciens, Lentilactobacillus kefiri, Lactococcus lactis, Geotrichum candidum, Pichia kudriavzevii and Starmerella sp.) settle early in the product and remain until the end of maturation with varying abundances throughout fermentation. Microbial counts increased during early fermentation stage, and remained stable during mid-fermentation, then declined during maturation. While microbial compositions were globally comparable between the two jars during mid-fermentation and maturation stages, differences between the two jars were mainly detected during early fermentation stage (D0 until D10). No significant sensorial differences were observed between the final products made in the two jars. Neither coliforms nor Enterobacteriaceae were detected in their viable state, starting D7 in both jars, suggesting the antimicrobial properties of the product.

Microbial communities and main features of labneh Ambaris, a traditional Lebanese fermented goat milk product

Labneh Ambaris is a traditional Lebanese dairy product typically made using goat milk in special earthenware jars. Its production is characterized by the regular additions of milk and coarse salt, all while draining the whey throughout a process that lasts for a minimum of 2 mo. In this study, 20 samples of labneh Ambaris, all produced by spontaneous fermentation, were studied. They were collected at the end of fermentation from different regions in Lebanon. Physicochemical and sensory properties were studied and microbial diversity was analyzed using culture-dependent and independent techniques. The V3-V4 region of the 16S rRNA gene and the ITS2 region were sequenced by DNA metabarcoding analyses for the identification of bacteria and yeast communities, respectively. Out of 160 bacterial and 36 fungal taxa, 117 different bacterial species and 24 fungal species were identified among all labneh Ambaris samples studied. The remaining ones were multi-affiliated and could not be identified at the species level. Lactobacillus was the dominant bacterial genus, followed by Lentilactobacillus, Lactiplantibacillus, Lacticaseibacillus, and Lactococcus genera, whereas Geotrichum and Pichia were the dominant fungal genera. The 20 samples tested had varying levels of salt, protein, and fat contents, but they were all highly acidic (mostly having a pH < 4). According to the sensory scores generated by classical descriptive analysis, all samples were described as having basic similar characteristics such as goat smell and flavor, but they could be differentiated based on various intensities within the same descriptors like salty and acidic. This work could be considered as a base toward obtaining a quality label for labneh Ambaris.

Artisanal Household Milk Pasteurization Is Not a Determining Factor in Structuring the Microbial Communities of Labneh Ambaris: A Pilot Study

Labneh Ambaris is a traditional Lebanese dairy product traditionally made using raw goat's milk in earthenware jars, but recently the use of artisanally pasteurized milk was introduced for safety reasons. In this study, 12 samples of labneh Ambaris were studied, six made using raw goat's milk and six others using artisanally pasteurized goat's milk. These samples were collected during fermentation and their microbial compositions were analyzed. The 16S V3-V4 and the ITS2 regions of the rDNA were sequenced by DNA metabarcoding analyses for the identification and comparison of bacterial and fungal communities, respectively. The samples had high microbial diversity but differences in samples microbiota were unrelated to whether or not milk was pasteurized. The samples were consequently clustered on the basis of their dominant bacterial or fungal species, regardless of the milk used. Concerning bacterial communities, samples were clustered into 3 groups, one with a higher abundance of Lactobacillus helveticus, another with Lactobacillus kefiranofaciens as the dominant bacterial species, and the third with Lentilactobacillus sp. as the most abundant species. Species belonging to the Enterobacteriaceae family were detected in higher abundance in all raw milk samples than in artisanally pasteurized milk samples. As for fungal communities, the samples were clustered into two groups, one dominated by Geotrichum candidum and the other by Pichia kudriavzevii.

Harnessing diversity of Lactococcus lactis from raw goat milk: Design of an indigenous starter for the production of Rocamadour, a French PDO cheese

Twenty-four strains of Lactococcus lactis isolated from raw goat milk collected in the Rocamadour PDO area were analysed by MLST typing and phenotypic characterisation. The strains were combined to design an indigenous starter for the production of Rocamadour PDO cheese. The strains were divided into three classes based on their technological properties: acidifying and proteolytic strains in class I (12/24 strains), slightly acidifying and non-proteolytic strains in class II (2/24 strains), and non-acidifying and non-proteolytic strains in class III (10/24 strains). Interestingly, all but three strains (21/24) produced diacetyl/acetoin despite not having citrate metabolism genes, as would classically be expected for the production of these aroma compounds. Three strains (EIP07A, EIP13D, and EIP20B) were selected for the indigenous starter based on the following inclusion/exclusion criteria: (i) no negative interactions between included strains, (ii) ability to metabolize lactose and at least one strain with the prtP gene and/or capable of producing diacetyl/acetoin, and (iii) selected strains derived from different farms to maximise genetic and phenotypic diversity. Despite consisting exclusively of L. lactis strains, the designed indigenous starter allowed reproducible cheese production with performances similar to those obtained with an industrial starter and with the sensory qualities expected of Rocamadour PDO cheese.

Effects of thermized donkey milk with lysozyme activity on altered gut barrier in mice exposed to water-avoidance stress

Nutrition plays a crucial role in human gut health through the improvement of gut barrier functionality. Donkey milk represents an interesting source of natural antimicrobial factors such as lysozyme. Recently, anti-inflammatory properties of donkey milk lysozyme activity were described in a mouse model of ileitis. The current increase of donkey milk consumption highlights the necessity to propose a healthy milk compliant with microbiological standards. This study aims to define a heat treatment of donkey milk, retaining its high lysozyme activity, and to evaluate its beneficial effects on a gut barrier impairment model due to chronic stress in mice. To perform this experiment, samples of raw donkey milk were collected in 15 distinct French farms. Microbiological analysis and lysozyme content and activity were evaluated for each sample. Then, several heat treatments were carried out to define a time and temperature combination that allowed for both a reduction in the number of total micro-organisms, increasing the shelf-life of the product, and preservation of lysozyme activity. The beneficial effect of heated donkey milk on the gut barrier of mice was evaluated and compared with raw donkey milk. We found that samples of raw donkey milk showed low total mesophilic microbial counts, and no pathogens were detected. Among the different heat-treatment procedures tested, a 2-min, 72°C combination was determined to be the most optimal time and temperature combination to preserve lysozyme activity and increase the shelf-life of donkey milk. Oral administration of this heat-treated donkey milk in mice counteracted chronic stress-induced intestinal damage, illustrated by gut hyper-permeability and low-grade inflammation, similar to raw donkey milk. We have demonstrated for the first time that oral intervention with donkey milk, optimally heat-treated to retain enzymatic lysozyme activity, improves intestinal barrier damage linked to psychological stress in mice.

French Brittany macroalgae screening: composition and methane potential for potential alternative sources of energy and products

Macroalgae are biomass resources that represent a valuable feedstock to be used entirely for human consumption or for food additives after some extractions (mainly colloids) and/or for energy production. In order to better develop the algal sector, it is important to determine the capacity of macroalgae to produce these added-values molecules for food and/or for energy industries on the basis of their biochemical characteristics. In this study, ten macroalgae obtained from French Brittany coasts (France) were selected. The global biochemical composition (proteins, lipids, carbohydrates, fibers), the presence and characteristics of added-values molecules (alginates, polyphenols) and the biochemical methane potential of these algae were determined. Regarding its biochemical composition, Palmaria palmata is interesting for food (rich in nutrients) and for anaerobic digestion (0.279 LCH4/gVS). Saccharina latissima could be used for alginate extraction (242 g/kgTS, ratio between mannuronic and guluronic acid M/G=1.4) and Sargassum muticum for polyphenol extraction (19.8 g/kgTS).

Transformation of zearalenone to zearalenone-sulfate by Aspergillus spp

The primary goal of this research was to assess the biotransformation of zearalenone (ZEA), an oestrogenic mycotoxin, into ZEA-sulfate by some Aspergillus section Nigri isolates. A. niger isolates were shown to be able to convert ZEA after 72 h of incubation at different ZEA concentrations (5 to 150 µg/ml). The product formula corresponding to ZEA-sulfate was determined by accurate mass measurement. This conjugate was shown to be less oestrogenic than ZEA using a MCF-7 proliferation assay. This study demonstrated that A. niger has the ability to transform ZEA over a broad range of ZEA concentrations (5 to 150 µg/ml) and that sulfonation could lead to a less toxic compound. These results are significant as little is known about the ability of fungi, and especially A. niger, to detoxify ZEA by sulfonation. This study could lead to a way of detoxifying feed naturally contaminated with mycotoxins.

Adsorption of zearalenone by Aspergillus japonicus conidia: new trends for biological decontamination in animal feed

Zearalenone (ZEA) is an oestrogenic mycotoxin produced by Fusarium spp. on a wide variety of grains. The presence of ZEA impairs farm animal health. In this study, the ability to remove ZEA by conidia of Aspergilli was evaluated in vitro. This mycotoxin was successfully eliminated in vitro by living and heat-treated conidia just after conidial inoculation, especially by Aspergillus japonicus Mu541 (IMI389204) conidia. Consequently, components involved in adsorption are not affected by heat-treatment. The influence of pH on ZEA removal was also determined. Results have shown that ZEA removal was 53% at pH 2 while 2% removal was observed at pH 11. Then, the adsorption capacity was evaluated in vitro in porcine gastrointestinal tract conditions. We observed that there was better adsorption in acidic stomach conditions. Finally, the phenomenon has been modelled using Hill's equation. This model was very suitable and confirmed better adsorption at acidic pH. Aspergilli section Nigri conidia were able to adsorb ZEA instantaneously especially in acidic conditions as in the stomach. The use of heat-treated conidia could be a very interesting means of decreasing ZEA levels in animal feed. It must now be assessed directly on naturally contaminated feed and on animals.