Probiotics can regulate the body’s immune system through both non-specific and specific immunity, thereby regulating host health. In terms of non-specific immune regulation, probiotics can activate the intrinsic immune system, regulate the mucosal barrier function, and play an immune role by influencing the activity of intrinsic immune cells such as macrophages, dendritic cells and natural killer cells, as well as their differentiation and maturation; in terms of specific immune regulation, probiotics play a role in regulating the immunoglobulin level and the maturation of B cells. Probiotics can also regulate T-cell differentiation according to the condition of the body, thus regulating specific immunity. Many studies have focused on the role of probiotics in metabolism and nutrition, and the mechanisms involved in the immunomodulatory role of probiotics have only been partially described. This review summarises the role of common probiotics such as Lactobacillus plantarum and Lactobacillus rhamnosus in immunomodulation as well as their mechanisms, describing the currently known mechanisms of immunomodulation by probiotics in improving the host immune system. A deeper understanding of probiotics and their specific mechanisms of action will facilitate the use of probiotics for immunomodulation in clinical medicine, functional foods, and other areas. This will also contribute to the development and research of engineered probiotics, next-generation probiotics, and other new functional probiotics with immunomodulatory effects.

Escherichia coli (E. coli) is an important pathogenic bacterium that needs to be monitored in the powdered infant formula (PIF) processing environment, and its acid resistance may compromise the cleaning effect, leading to an increase in the prevalence rate. In this study, 56 E. coli strains were isolated from 1,130 samples collected in 8 PIF factories, and strains were classified into 19 STs. The strain EC56 with the strongest acid resistance was selected for transcriptome and proteome sequencing. The correlation analysis results indicated that EC56 mainly enhanced acid resistance through the regulation of two systems: glutamate-dependent acid-tolerance (Gad) and ornithine dependent acid-tolerant (Orn). In addition, the expression of acid shock protein (asr gene), which can prevent cell inactivation under acid stress, and DNA protection during starvation protein (dps gene), which can bind to DNA and protect DNA from acid-induced strand breaks, was significantly upregulated. The downregulation of the OmpF (ompF gene) and tryptophanase (tnaA gene) also enhanced the acid resistance of bacteria. Fortunately, the expression levels of most virulence factors of E. coli, especially those related to motility function, were significantly downregulated after acid stress. This study reveals the molecular regulatory mechanism to acid stress and the changes in virulence factors of E. coli in the PIF processing environment, which is helpful for production enterprises to carry out hazard prevention and control and predict the changes in bacterial pathogenicity.

As the demand for dairy products increases, the issue of their safety has aroused widespread concern. Real-time, rapid and accurate detection of pathogenic factors in milk is an important guarantee for solving this issue. In recent years, the development of lateral flow immunochromatographic assays (LFIA) has provided good conditions for on-site detection of pathogenic factors in dairy products. This article describes the principle of LFIA for the monitoring of pathogenic factors in milk, and reviews the current status of the application of chromogenic reaction enhancement strategies, and new nanomaterials alone or combined with nucleic acid amplification and smartphone technology for sensitivity enhancement. Meanwhile, two major high-throughput detection methods, the multi-line and multi-strip ones, are summarized. We hope that this review will provide important theoretical guidance for rapid, highly sensitive and high-throughput field monitoring of pathogenic factors in milk.

Postbiotics are dead bacteria without vital signs and their metabolites. Since many substances in postbiotics are still biologically active and are safer and more stable than probiotics, they are widely used in the prevention and treatment of various diseases. In recent years, many studies have shown that postbiotics can ameliorate obesity by regulating lipid metabolism, which are expected to be a new strategy for the prevention and treatment of obesity. This article introduces the harms and possible pathogenesis of obesity, illustrates the potential mechanism by which postbiotics regulate diseases, and reviews the role of postbiotic bacteria and their metabolites in obesity regulation. This article is expected to provide references for future research on the application of postbiotics in obesity management.

Food allergy (FA) is an aberrant immune response triggered by the ingestion of a food antigen. Ovalbumin (OVA)-sensitized and challenged BALB/c mice were orally administered heat-killed (HK)-Lactobacillus paracasei JY56. In this work, HK-L. paracasei JY56 alleviated the FA-induced decrease in body weight and rectal temperature and reduced the allergy score. Serum analysis showed that HK-L. paracasei JY56 reduced the levels of specific antibodies (OVA-specific Immunoglobulin E (sIgE) and OVA-specific Immunoglobulin G (sIgG)) and allergic mediators (histamine and mast cell protease) in FA mice. In addition, HK-L. paracasei JY56 also could alleviate OVA-induced FA by suppressing T helper (Th)2 and Th17-type immune responses, which was evidenced by the regulation of splenic lymphocyte subpopulations and associated cytokine secretion. Moreover, jejunal histological analysis and intestinal barrier function related gene expression measurement were performed to verify the intestinal barrier repair of HK-L. paracasei JY56. Meanwhile, the TLR4/NF-κB inflammatory pathway activation was inhibited by HK-L. paracasei JY56 at gene and protein levels. Finally, HK-L. paracasei JY56 was performed to modulate the gut microbiota structure and increase the levels of short-chain fatty acids. In conclusion, HK-L. paracasei JY56 could alleviate OVA-induced FA in multiple ways, and this study provides a theoretical basis for the application of inactivated probiotics in functional foods for FA.

Cronobacter spp. has strong resistance to desiccation and high permeability in Enterobacteriaceae, and powdered infant formula (PIF) is one of the main contamination routes. In recent years, the contamination of Cronobacter spp. in PIF incidents occurs from time to time, causing infant serious diseases or death. In this investigation, matrix-assisted laser desorption/ionization time of flight mass spectrometry was used to identify the phenotypes of 35 Cronobacter strains isolated from PIF and its processing environment. Subsequently, the isolates were evaluated for drying and osmotic pressure tolerance. The results showed that the deactivation rate of the strains ranged from 9.01% to 77.57%, and the highest osmotic pressure condition the strains could tolerate was 6 g/100 mL NaCl. In addition, there was a positive correlation between biofilm formation ability and desiccation resistance. Combined with transcriptomics, Cronobacter spp. could activate biofilm synthesis, produce more trehalose, accumulate betaine and electrolytes to stabilize intracellular structure under the two treatment conditions. A total of 31 and 43 genes were found related to desiccation and permeability resistance, respectively. And some genes (cysM, thuF, ycjO, etc.) were found to be associated with two tolerances for the first time.

Branched-chain fatty acids (BCFAs) are new bioactive fatty acids with anti-inflammatory properties. However, the role of BCFAs in alleviating ulcerative colitis has not been clarified. Herein, we evaluated the protective effect of BCFAs from goat milk in mice with colitis induced using dextran sodium sulfate (DSS) and explored the corresponding mechanism. These results show that BCFAs extracted from goat milk can significantly alleviate weight loss in mice, and reduce the disease activity index and the activity of myeloperoxidase while increasing the content of antioxidant enzymes in colon tissue and reducing the oxidation stress response. These data also show that BCFAs can down-regulate the gene and protein expression of the toll-like receptor 4 (TLR4)/ nuclear factor κB p65 (NF-κB p65)/NOD-like receptor thermal protein domain associated protein 3 (NLRP3) signaling pathway, and at the same time significantly reduce the expression of pro-inflammatory factors tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and IL-18 in colon tissue, and significantly increase the expression of the anti-inflammatory factor IL-10. In conclusion, these results demonstrated that BCFAs in goat milk exerted effects on colitis-related inflammatory cytokines and inhibited inflammation by inducing the TLR4/NF-κB/NLRP3 pathway to alleviate DSS-induced ulcerative colitis. This study provides evidence for the potential of BCFAs as bioactive fatty acids in food products and to ameliorate ulcerative colitis development in mice.

Oxidative stress is one of the main ways to cause alcohol-induced liver injury, and alcoholic liver disease (ALD) has been a common health problem worldwide. Lactic acid bacteria (LAB) is also considered as a potential treatment to alleviate alcohol-induced liver injury. Lactobacillus plantarum J26 is a LAB isolated from Chinese traditional fermented dairy products with excellent probiotic effects. This study aimed to establish a mice model of alcoholic liver injury through acute-on-chronic alcohol feeding and to study the alleviating effect of pre-intake of L. plantarum J26 on alcohol-induced oxidative liver injury and focus on its potential mechanism of alleviating effect. The results showed that pre-intake of L. plantarum J26 could improve liver pathological changes, reduce lipid accumulation, increase mitochondrial ATP and mitochondrial (mtDNA) levels, and alleviate liver injury. In addition, pre-intake L. plantarum J26 can improve the level of short-chain fatty acids (SCFAs) in the intestines in mice, short chain fatty acids can be used as a signaling molecule activation of nuclear factor E2-related factor 2 (Nrf2) signaling pathway to alleviate liver oxidative stress, and maintain mitochondrial homeostasis by regulating the expression of genes related to mitochondrial dynamics and autophagy, thereby reducing cell apoptosis to alleviate alcohol-induced oxidative liver injury.