Food microbiology最新文献

This study was designed to evaluate the combination effects of antimicrobial peptides (FK13 and FK16) and phage-encoded endolysin (LysPB32) on the inhibition of growth of polymyxin B-resistant Salmonella Typhimurium ATCC 19585 (ST^PMB). The inhibitory effects of FK13, FK16, and LysPB32 against ST^PMB were evaluated by using antimicrobial susceptibility, membrane permeability, biofilm reduction, cross-resistance, and mutant frequency assay. The minimum inhibitory concentrations (MICs) of FK13 and FK16 treated with LysPB32 (FK13+LysPB32 and FK16+LysPB32) against ST^PMB were decreased from more than 512 to 128 μg/ml and from 64 to 32 μg/ml, respectively. Compared to the control, the number of ST^PMB in the growing culture was reduced by 4.2 and 5.2 log CFU/ml, respectively, for FK13+LysPB32 and FK16+LysPB32 after 12-h incubation at 37 °C. All treatments (FK13, FK16, FK13+LysPB32, FK16+LysPB32) significantly increased the permeability of the outer membrane of ST^PMB. Biofilms were significantly decreased from OD₆₀₀ of 0.6 to 0.16 for FK13+LysPB32 and from 0.6 to 0.13 for FK16+LysPB32. The ratios of MICs of erythromycin, ceftriaxone, polymyxin B, and ciprofloxacin to MIC of the control against ST^PMB were decreased to 0.50 for FK13+LysPB32 and FK16+LysPB32. The bactericidal activities of amikacin and gentamicin were enhanced for FK13+LysPB32 and FK16+LysPB32 (2-fold < MBC/MIC ratio). The mutant frequencies of ST^PMB to antibiotics were decreased when treated with FK13+LysPB32 and FK16+LysPB32. The results suggest that the combination of antimicrobial peptides and endolysins can be a promising strategy to control polymyxin B-resistant S. Typhimurium.

Clostridium perfringens, as a foodborne pathogen, can cause various intestinal diseases in both humans and animals according to its repertoire of toxins. In recent years, a multitude of studies have highlighted its threat to infants and young children. C. perfringens carries numerous toxins, with the newly identified BEC toxin confirmed as the second toxin to cause diarrheal illness, after CPE. However, the global dissemination of C. perfringens strains carrying becAB genes, which encode BEC toxins, has not been extensively studied. Following epidemiological surveillance of the prevalence of C. perfringens from different sources in various provinces of China, we identified two becAB-carrying strains and one strain carrying a sequence similar to becAB from distinct provinces and sources. When combined with genomic analysis of other becAB-carrying C. perfringens strains from public databases, we found that becAB was present in strains from different lineages. Our analysis of the plasmid and genetic environment corroborates previous findings on becAB-carrying strains, confirming that it currently achieves horizontal transmission through one type of evolutionarily conserved Pcp plasmid. This study provides a comprehensive analysis of the prevalence and transmission patterns of the newly emerged toxin gene locus, becAB, in C. perfringens. Despite the relatively low identification rate of becAB-carrying strains, their potential impact requires ongoing surveillance and investigation of their features, particularly their antimicrobial resistance.

Despite numerous studies evaluating the antimicrobial activity of essential oil components (EOCs) against different microorganisms, the effect of the composition of the matrix in which they are applied remains unexplored. Hence, the effect of different food components (i.e., proteins, lipids, carbohydrates, acids, ethanol) on vanillin antimicrobial activity was carried out by assessing the growth of E. coli at different incubation times (0, 1, 4, 8 and 24 h). Based on these outcomes, the food components that most adversely affected vanillin antimicrobial activity were subsequently tested with four other EOCs (i.e., carvacrol, eugenol, geraniol, thymol). The effective concentration of antimicrobials after coming into contact with food components was quantified. The results indicated that bovine serum albumin (BSA), sunflower oil and carbohydrates partially or completely inhibited the antimicrobial efficacy of the tested EOCs, and the inhibition rate depended on the specific EOC-food component combination. Geraniol was notably the most efficient with BSA present. Eugenol performed best with sunflower oil. Carvacrol, eugenol, geraniol and thymol were more effective than vanillin with D-lactose present. This study confirmed that loss of EOCs’ effective concentration due to an interaction with food constituents is a significant cause of antimicrobial activity inhibition. These findings underscore the importance of considering matrix composition when selecting antimicrobials to combat a particular strain in real food applications.

A variety of methods exists for typing bacteria. However, guidelines for the application and interpretation of typing tools in epidemiologic investigations of Staphylococcus aureus are lacking. This study aimed to identify appropriate typing methods for S. aureus population studies and outbreak investigation. We compared pulsed-field gel electrophoresis (PFGE), seven loci multi-locus sequence typing (MLST), core genome MLST (cgMLST), core single nucleotide polymorphism (cSNP), and enterotoxin (se/SE) profiles on 351 S. aureus isolates. The discriminatory power, concordance, and congruence of typing results were assessed. cgMLST, cSNP, and PFGE yielded the highest discrimination value, followed by se/SE typing and MLST. The best concordance of results was found between cgMLST and cSNP, while the best congruence was observed for cgMLST and cSNP with all methods, followed by PFGE with MLST. The strengths and weaknesses of each method are highlighted. For population structure, cgMLST and cSNP performed better than PFGE and MLST in terms of resolution of clusters and in phylogenetic inference. Enterotoxin profiles matched with MLST groups, suggesting the use of se/SE typing to predict MLST results. For the retrospective analysis of 31 outbreaks, all methods performed almost equally to discriminate epidemiologically related strains and can be used to unambiguously distinguish outbreak strains.

Polygonum hydropiper (PH) is a rich source of active compounds and serves as a pivotal ingredient in Chinese rice wine (Huangjiu) production. This study investigates the impact of PH and Polygonum hydropiper extract (PHE) on ethyl carbamate (EC) production during Huangjiu fermentation. Our findings reveal that PH enhances the relative abundance of Bacillus subtilis in Huangjiu fermentation, thereby facilitating its interaction with Saccharomyces cerevisiae. Furthermore, PH modulates the urea metabolism of S. cerevisiae. In the PH-B. subtilis-S. cerevisiae fermentation system, the expression of DUR1,2 and DUR3 genes in S. cerevisiae is upregulated. This augmentation leads to increased urea uptake and metabolism by S. cerevisiae in the fermentation broth, subsequently reducing the urea concentration in the fermentation medium (The EC content in the CK group was approximately 355.55 % and 356.05 % higher than those in the PH and PHE groups, respectively). Consequently, PH demonstrates promise in reducing the EC concentration of Huangjiu, offering a novel approach to enhance the safety of Huangjiu consumption.

This study investigated various strategies: mono-, simultaneous and sequential fermentation of halophilic Candida versatilis and Tetragenococcus halophilus to valorize salted whey, a side stream of salted tofu (pressed beancurd) production, with an ultimate goal of creating a soy sauce-like condiment. Growth, glucose, organic acids were monitored throughout fermentation, while free amino acids and volatile compounds were analyzed on the final days. In monoculture fermentation, both C. versatilis and T. halophilus thrived in salted soy whey. However, in co-culture fermentation, an antagonistic relationship was observed, wherein C. versatilis growth was slightly suppressed and T. halophilus was significantly inhibited. In C. versatilis-involved fermentations, no significant (p > 0.05) differences in key volatile and non-volatile chemical components were found among various fermentation modes. Key soy sauce-like volatile compounds, such as 4-ethylguaiacol and 4-ethylphenol, were detected in all C. versatilis-fermented salted soy whey, while T. halophilus primarily functioned as a lactic and acetic acids producer. This study highlights the potential of mixed culture fermentation involving soy sauce yeast and lactic acid bacteria for eventually developing a soy sauce-like condiment from salted soy whey, with C. versatilis playing a crucial role in flavour development. The findings suggest that fermenting of a single culture of C. versatilis in lactic acid-adjusted salted soy whey could be a viable and efficient choice for future production of soy sauce-like condiment.

Environmental conditions significantly impact the metabolism of Saccharomyces cerevisiae, a Crabtree-positive yeast that maintains a fermentative metabolism in high-sugar environments even in the presence of oxygen. Although the introduction of oxygen has been reported to induce alterations in yeast metabolism, knowledge of the mechanisms behind these metabolic adaptations in relation to redox cofactor metabolism and their implications in the context of wine fermentation remains limited. This study aimed to compare the intracellular redox cofactor levels, the cofactor ratios, and primary metabolite production in S. cerevisiae under aerobic and anaerobic conditions in synthetic grape juice. The molecular mechanisms underlying these metabolic differences were explored using a transcriptomic approach. Aerobic conditions resulted in an enhanced fermentation rate and biomass yield. Total NADP(H) levels were threefold higher during aerobiosis, while a decline in the total levels of NAD(H) was observed. However, there were stark differences in the ratio of NAD⁺/NADH between the treatments. Despite few changes in the differential expression of genes involved in redox cofactor metabolism, anaerobiosis resulted in an increased expression of genes involved in lipid biosynthesis pathways, while the presence of oxygen increased the expression of genes associated with thiamine, methionine, and sulfur metabolism. The production of fermentation by-products was linked with differences in the redox metabolism in each treatment. This study provides valuable insights that may help steer the production of metabolites of industrial interest during alcoholic fermentation (including winemaking) by using oxygen as a lever of redox metabolism.

Volatile organic compounds (VOCs), a byproduct of mold metabolism, have garnered increasing interest because the VOCs can be used to detect food early contamination. So far, the use of VOCs as indicators of rice mildew, specifically caused by Aspergillus tubingensis and Penicillium oxalicum, and the mechanisms of their generation are not well investigated. This study examines the VOCs produced by these molds during paddy storage, utilizing headspace solid-phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC–MS). We further elucidate the mechanisms underlying the formation of these VOCs through a comparative transcriptomic analysis. The VOCs characteristic to A. tubingensis and P. oxalicum, identified with a VIP value > 1 in the partial least squares discriminant analysis (PLS-DA) model, are primarily alkenes. Our transcriptome analysis uncovers key metabolic pathways in both molds, including energy metabolism and pathways related to volatile substance formation, and identifies differentially expressed genes associated with alkane and alcohol formation.

The demand for natural products has significantly increased, driving interest in carotenoids as bioactive compounds for both human and animal consumption. Carotenoids, natural pigments with several biological properties, like antioxidant and antimicrobial, are increasingly preferred over synthetic colorants by the consumers (chemophobia). The global carotenoid market is projected to reach US$ 2.45 billion by 2034, driven by consumer preferences for natural ingredients and regulatory restrictions on synthetic products. Among carotenoids, bacterioruberin (BR), a C₅₀ carotenoid naturally found in microbial hyperhalophilic archaea and in moderate halophilic archaea, stands out for its exceptional antioxidant capabilities, surpassing even well-known carotenoids like astaxanthin. BR's and its derivatives unique structure, with 13 conjugated double bonds and four -OH groups, contributes to its potent antioxidant activity and potential applications in food, feed, supplements, pharmaceuticals, and cosmeceuticals. This review explores BR's chemical and biological properties, upstream and downstream technologies, analytical techniques, market applications, and prospects in the colorants industry. While BR is not intended to replace existing carotenoids, its inclusion enriches the range of natural products available to meet the rising demand for natural alternatives. Furthermore, BR's promising antioxidant capacity positions it as a key player in the future carotenoid market, offering diverse industries a natural and potent alternative for several applications.

Escherichia coli O157:H7 is a pathogenic serotype of Escherichia coli. Consumption of food contaminated with E. coli O157:H7 could cause a range of diseases. Therefore, it is of great importance to establish rapid and accurate detection methods for E. coli O157:H7 in food. In this study, based on LAMP and combined with the CRISPR/cas12a system, a sensitive and specific rapid detection method for E. coli O157:H7 was established, and One-Pot detection method was also constructed. The sensitivity of this method could stably reach 9.2 × 10° CFU/mL in pure culture, and the whole reaction can be completed within 1 h. In milk, E. coli O157:H7 with an initial contamination of 7.4 × 10° CFU/mL only needed to be cultured for 3 h to be detected. The test results can be judged by the fluorescence curve or by visual observation under a UV lamp, eliminating instrument limitations and One-Pot detection can effectively prevent the problem of false positives. In a word, the LAMP-CRISPR/cas12a system is a highly sensitive and convenient method for detecting E. coli O157:H7.