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Camel milk is a nutrient-rich diet and fermentation affects its nutritional value and probiotic function. In this study, sour camel milk and oat jujube sour camel milk were prepared using fermentation bacteria agent TR1, and the metabolites of camel milk, sour camel milk and oat jujube sour camel milk were detected using a non-targeted metabolomics approach using liquid chromatography-mass spectrometry (LC-MS).The results showed that the partial least squares discriminant analysis (PLS-DA) with 100 % accuracy and good predictive power detected 343 components in positive ion mode and 220 components in negative ion mode. The differential metabolites were mainly organic acids, amino acids, esters, vitamins and other substances contained in camel milk.It showed that there were significant differences in the metabolites of camel milk, sour camel milk and oat jujube sour camel milk. Based on the pathway enrichment analysis of the three dairy products in the KEGG database, 12 metabolic pathways mainly involved in the positive ion mode and 20 metabolic pathways mainly involved in the negative ion mode were identified. The main biochemical metabolic pathways and signal transduction pathways of the differential metabolites of the three dairy products were obtained. This study provides theoretical support for improving the nutritional quality and probiotic function of camel milk and fermented camel milk products and provides a basis for the development of relevant processing technologies and products for camel milk and fermented camel milk.

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Camel milk produces many beneficial functional compounds and affects body health through metabolism. The differential metabolites of bactrain camel milk in Alxa before and after fermentation were identified by liquid chromatography-tandem mass spectrometry based metabolomics (LC-MS/MS). The differential metabolite pathway types were also identified in this paper. We obtained the following results that 148 and 82 differential metabolites were detected in positive and negative ion mode respectively, 85 differential metabolites were shown a significant upward trend and 63 with downward trend after fermentation in positive ion mode. Meanwhile, 32 differential metabolites characterized upward trend and 50 characterized downward trend in negative ion mode. The differential metabolites were mainly organic acids, amino acids, esters, vitamins and other substances contained in camel milk. Among them, most up-regulated substances had the functions of lowering blood pressure, lowering blood sugar, treatment of inflammation, antibiosis and other effects. Many harmful substances were significantly down-regulated after camel milk fermentation. However, there were also some metabolites whose prebiotic functions have been weakened by camel milk fermentation, which may provide reference values for healthcare function, exploitation and application of camel milk.

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Quantum dots (QDs) as potent candidates possess advantageous superiority in fluorescence imaging applications, but they are susceptible to the biological circumstances (e.g., bacterial environment), leading to fluorescence quenching or lose of fluorescent properties. In this work, CdTe QDs were embedded into mesoporous silica nanospheres (m-SiO2 NSs) for preventing QD agglomeration, and then CdTe QD-embedded m-SiO2 NSs (m-SiO2/CdTe NSs) were modified with Ag nanoparticles (Ag NPs) to prevent bacteria invasion for enhanced anticounterfeit applications. The m-SiO2 NSs, which serve as intermediate layers to combine CdTe QDs with Ag NPs, help us establish a highly fluorescent and long-term antibacterial system (i.e., m-SiO2/CdTe/Ag NSs). More importantly, CdTe QD-embedded m-SiO2 NSs showed fluorescence quenching when they encounter bacteria, which was avoided by attaching Ag NPs outside. Ag NPs are superior to CdTe QDs for preventing bacteria invasion because of the structure (well-dispersed Ag NPs), size (small diameter), and surface charge (positive zeta potentials) of Ag NPs. The plausible antibacterial mechanisms of m-SiO2/CdTe/Ag NSs toward both Gram-positive and Gram-negative bacteria were established. As for potential applications, m-SiO2/CdTe/Ag NSs were developed as fluorescent anticounterfeiting ink for enhanced imaging applications.

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Novel N-halamine nanoparticles potentially useful for killing pathogenic bacteria, i.e., SiO2@PS/N-halamine NPs, were successfully synthesized via the immobilization of N-halamines onto the polystyrene-coated silica nanoparticles (SiO2@PS NPs). The effect of reaction conditions, i.e., chlorination temperature, bleaching concentration, chlorination time, on the oxidative chlorine content in the products was systematically investigated. The antibacterial activity of the products was tested via the modified plate counting methd using Escherichia coli (E. coli) as a model bacterium. The possible mechanism of the antibacterial action of the products was also studied using scanning electron microscopy combined with a inhibition zone study. The antimicrobial capability of the products was well controlled by tuning the oxidative chlorine content in the products. More importantly, the role of DksA protein in the susceptibility of E. coli against the products was proven using a time-kill assay. This in-depth investigation of the sensitivity of E. coli towards N-halamine NPs provides a systematic understanding of the utility of N-halamines for deactivating bacteria or even disease control.

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