Gwénaël Jan

MicroRNAs (miRNAs) are small regulatory RNAs that regulate numerous biological processes and potentially impact human health. Despite their abundance in raw milk, little is known about their content in processed dairy products or how manufacturing affects their abundance and bioavailability. We characterized and compared the miRNA profiles of yogurt and cheese produced from the same raw milk from cows raised under agroecological or intensive systems, assessing compositional changes during processing, while accounting for farming system effects. High-throughput sequencing identified a total of 1,384 miRNAs, including 258 common to all matrices, forming a conserved milk-derived core. Processing into yogurt or cheese reduced milk-specific miRNAs while introducing microbial small RNAs from fermentation bacteria such as Lactococcus and Streptococcus thermophilus. Differential analysis revealed stable miRNomes across agroecological and intensive farming systems, but substantial processing-associated changes involving 29 and 353 miRNAs during cheese and yogurt production, respectively, and some miRNAs showed matrix-specific stability. These miRNAs were predicted to influence cell proliferation, metabolism, and protein-related pathways, suggesting shifts in the regulatory impact of milk-derived miRNAs in fermented dairy products. Overall, these findings underscore the dynamic nature of dairy miRNomes and the combined influence of processing and microbial activity in shaping miRNA composition.

Dairy products are major dietary sources of B vitamins. However, the impact of cow diet and dairy processing techniques on B vitamin concentrations remains unclear. This study investigated the effects of diet composition on B-vitamin content in raw milk and, in yogurt, and Cantal-type cheese produced therefrom. Forty Holstein and Montbéliarde-breed cows were assigned to either a grass-based agroecological system or a corn-based intensive system for 19 weeks. Vitamins B1, B2, B5, and B6 were quantified by liquid chromatography, and B9 and B12 by chemiluminescence. Milk from the agroecological system contained higher vitamin B2, and lower vitamin B5 concentrations than milk from the intensive system. This same pattern was also observed in cheese, but not in yogurt, showing impacts of technological processing. Adding probiotics into yogurts increased pyridoxal (B6) concentration. This study highlighted diet-related differences in B vitamin concentrations in raw milk, and these differences transferred to cheese but not to yogurt.

The bacterial cell envelope is a complex structure composed of proteins, lipids, and other molecules that form the physical boundary between bacteria and the environment. In the gut microbiome, commensal bacteria play a fundamental role in maintaining intestinal homeostasis and modulating host physiology. Due to their strategic location, bacterial cell envelope components interact directly with the host immune system, intestinal cells, mucus, and other gut structures, leading to diverse biological effects. Even though beneficial bacteria produce effector molecules, the functional diversity of these molecules, especially among gut bacteria, remains largely unknown. This review compiles current knowledge on the structure and function of bacterial cell envelope components, with a specific focus on gut microbiome commensals and their role in host interactions. It highlights key effector molecules, their immunological recognizers, and the downstream mechanisms involved in such microbial-host interactions, in addition to stating important knowledge gaps. Identifying and characterizing these molecular interactions is a crucial step toward developing novel biotherapeutic targets, particularly for inflammatory bowel diseases and other gut-related disorders. By reviewing current findings and outlining key research deficits, this review deepens our understanding of how bacterial cell envelope components shape host-microbe interactions.

The gut microbiome plays a critical role in health, disease and immunity. To date, we have access to large datasets describing how the microbial diversity present in the gut correlates with many clinical conditions. However, the microbiome composition is taxonomically complex; influenced by many environmental factors; and variable between individuals and communities, thereby limiting functional and mechanistic insights into the microbiota‒host interactions. We are still unsure of the molecular mechanisms by which gut commensal microbes intrinsically possess to interact with the immune system and induce beneficial responses. This study has addressed this important question by revealing that only certain members of Lactobacillaceae, a bacterial family very well known for its probiotic properties, interact very intimately with macrophages because of their ability to simultaneously overexpress adhesive cell wall proteins and to self-aggregate, leading to significant production of type I interferon (IFN-I) cytokines. IFN-I cytokines are essential to confer protection against viral infections and auto-immune disorders. Specifically, we have proved that this enhanced IFN-I feature is strain-dependent and predominantly driven by cGAS, a molecule that activates the cytosolic sensor STING upon the recognition of bacterial DNA. Furthermore, another cytosolic sensor, NOD2, seems to be an additional stimulus to amplify IFN-I production, suggesting the involvement of successive molecular events for a prominent probiotic response. Our findings provide insight into how specific molecules of probiotic bacteria modulate or stimulate host responses, providing a better understanding of the molecular crosstalk between the microbiome and immune cells.

Starters were selected on their ability to modulate immune response. Developed innovative fermented soymilk further modulated human immune cells, protected epithelial barrier integrity and mitigated colitis in vivo.

Microbial agents have promise for the bioremediation of Pb(II)-polluted environments and wastewater, the biodecontamination of foods, and the alleviation of toxicity in living organisms. The dairy bacterium Propionibacterium freudenreichii is poorly able to remove Pb(II) from aqueous solution at 25 ppm, ranging from 0 to 10% of initial concentration. Here, we report on an original strong enhancement of this activity (ranging from 75% to 93%, p < 0.01) following the addition of a polysorbate detergent (Tween^® 80) during or either shortly after the growth of a P. freudenreichii culture. We evaluated the optimal Tween^® 80 concentration for pretreatment conditions, documented the role of other detergents, and explored the possible mechanisms involved. Our results reveal a novel, environmentally friendly, low-cost pretreatment procedure for enhancing the selective removal of lead from water by probiotic-documented bacteria.