Project description:BackgroundLactic acid bacteria (LAB) are used as starters in a wide variety of food fermentations. While the number of reports of phages infecting other LAB steadily increased over the years, information about phage associated with Latilactobacillus sakei, a frequently used meat starter, remains scarce.ResultsIn this study, a predictive genomic analysis of 43 Latilactobacillus sakei genomes revealed the presence of 26 intact, eleven questionable and 52 incomplete prophage sequences across all analysed genomes with a range of one to five predicted prophage sequences per strain. Screening 24 sakei strains for inducible prophages by utilising UV light or mitomycin C, we identified seven lysogenic strains showing lysis after induction during subsequent growth monitoring. Electron microscopic analysis revealed fully assembled virions in the purified lysates of four samples, thus confirming successful prophage induction. All virions featured icosahedral, isomeric heads and long, most likely non-contractile tails indicating siphoviruses. By performing phylogenetic analyses with various marker genes as well as full prophage sequences, we displayed a remarkably high diversity of prophages, that share a similar gene module organisation and six different chromosomal integration sites were identified. By sequencing viral DNA purified from lysates of Latilactobacillus sakei TMW 1.46, we demonstrate that simultaneous induction of multiple prophages is possible.ConclusionsWith this work, we not only provide data about the incidence of prophages harboured by the meat starter Latilactobacillus sakei, we also demonstrated their potential to impact growth of their host after induction, as well as forming seemingly fully assembled virions.
Project description:The autochthonous strain Latilactobacillus sakei sp. sakei ACU-2 was selected as a meat starter culture for dry sausage production. Transferring this strain from laboratory scale to industry requires an increase in biomass production, while lowering process costs. In this study, a combination of techniques was applied in order to optimize the culture medium composition to enhance biomass production of L. sakei ACU-2. One variable at a time experiments, Plackett-Burman design, and mixture design were performed to fulfill the strain nutritional requirements. Eventually, the optimized formulation contained 19.46 g/L yeast extract; 8.28 g/L whey protein concentrate; 2.26 g/L soy peptone; 30 g/L cerelose; 1 g/L Tween 80; 5 g/L sodium acetate; 0.2 g/L magnesium sulfate and 0.05 g/L manganese sulfate. When L. sakei ACU-2 was cultivated in a bioreactor using the alternative medium, an enhancement of 75.5% of biomass production was achieved, in comparison to its growth in the commercial de Man, Rogosa, and Sharpe medium. Furthermore, a reduction of 62-86% of the cost was also attained. These results support a promising large-scale application of the designed medium for high biomass yields of the starter culture at minor costs.
Project description:Kimchi is a traditional Korean food widely recognized for its probiotic properties and potential health benefits. Several lactic acid bacteria (LAB) from Kimchi exhibit immunomodulatory properties, and their efficacy has been evaluated for various immune-related diseases. However, the mechanisms underlying the immunomodulatory effects of LAB are not yet fully understood. In this study, we demonstrated the immunomodulatory effects of Latilactobacillus sakei Wikim0185, isolated from sweet potato Kimchi, in an ovalbumin (OVA)-induced allergic asthma mouse model by inducing tolerogenic dendritic cells (DCs) and regulatory T cells (Tregs). Bone marrow-derived dendritic cells (BMDCs) and OVA-peptide-stimulated splenocytes isolated from OT-II mice co-cultured with Wikim0185 exhibited increased secretion of the anti-inflammatory cytokine IL-10. Oral administration of Wikim0185 in allergic asthma experimental mice alleviated symptoms, including airway hyperresponsiveness (AHR), leukocyte infiltration, and reduced Th2-type cytokine levels in bronchoalveolar lavage (BAL) fluid. Notably, Wikim0185-treated mice displayed an increased proportion of Foxp3+ Tregs in mediastinal lymph nodes. Additionally, mediastinal lymph node cells restimulated with OVA exhibited decreased secretion of Th2-type cytokines while showing increased IL-10 production. Interestingly, RNA sequencing and chromatin immunoprecipitation (ChIP)-qPCR analysis revealed that Wikim0185 induced tolerogenic DCs through epigenetic histone modifications, increasing active chromatin marks (H3K4me3, H3K9ac, and H3K27ac) on the promoter regions of tolerogenic marker genes (Pdl1, Il10, Socs1, and Socs3). These findings suggest that Wikim0185 modulates immune responses by epigenetically reprogramming DCs, thereby promoting Treg differentiation and suppressing excessive Th2 immune responses in an allergic asthma mouse model.