International journal of food microbiology最新文献

Elaeagnus moorcroftii Wall. ex Schlecht (EWS) as a suitable food matrix contains abundant flavonoids for promoting human health, this study aimed to use flavonoid-targeted metabolomics and transcriptome sequencing to investigate the transformation of flavonoids in EWS juice (EWSJ) by mono- and mixed-cultures fermentations of Bifidobacterium animalis subsp. lactis HN-3 (B.an3) and Lacticaseibacillus paracasei YL-29 (L.cp29). A total of 33 flavonoids were identified in mono- and mixed-cultures fermented EWSJ. Among them, fermentation by B.an3 produced specific deglycosylation products (kaempferol (17.6 mmol/L) and luteolin (4.5 mmol/L)) and methoxylation products (syringaldehyde (59.05 mmol/L)), and fermentation by L.cp29 resulted in a specific deglycosylation product (quercetin (9.2 mmol/L)). The co-culture fermentation further increased the levels of isorhamnetin (52.3 mmol/L), and produced a specific product (homoplantaginin (0.03 mmol/L)), which significantly increased the bioactive-form flavonoids. Moreover, we analyzed changes in different flavonoid metabolites and differential genes before and after fermentation. After L.cp29 fermentation the expression of glycoside hydrolases and oxidoreductases were increased compared to other groups. After B.an3 fermentation the expression of isomerases and synthetases were increased compared to other groups. In particular, 6-phosphogluconolactonase (Pgl) and glucose-6-phosphate isomerase (Pgi) were increased in B.an3 fermentation. Thus, we validated the predicted transformation reactions by the biotransformation of flavonoids by the collected strains and crude enzyme extracts of B.an3 and L.cp29. These findings provided a basis for the development of functional plant-based foods with enhanced bioactive flavonoids.

β-Galactosidases can be used to degrade lactose in milk to prepare lactose-free milk, which is sweeter than ordinary milk and suitable for people with lactose intolerance. The β-galactosidase gene (WcGal2809) was cloned from Weissella confusa SW1 and successfully expressed in Escherichia coli BL21(DE3). The active WcGal2809 was identified to be a heterodimer composed of two distinct proteins LacL (72.4 kDa) and LacM (33.2 kDa), and it belonged to glycoside hydrolase family 2. The purified WcGal2809 showed the maximum activity at 25 °C and pH 7.0 for o-nitrophenyl-β-D-galactopyranoside (oNPG). WcGal2809 was strongly activated by Mn²⁺, Mg²⁺, and Fe²⁺, and significantly inhibited by Zn²⁺, Cu²⁺, and Ni⁺. The activity of WcGal2809 decreased quickly after incubation at 40 °C or higher temperature, suggesting it was a cold-adapted enzyme. Additionally, 6 U of WcGal2809 could hydrolyze 85.23 % of the lactose in 1 mL of milk at 25 °C after incubation for 48 h, while 2 U of WcGal2809 could hydrolyze 74.40 % of the lactose in 1 mL of milk at 25 °C after incubation for 7 d. Taken together, WcGal2809 is a promising industrial biocatalyst for efficiently hydrolyzing lactose in milk at room temperature during milk storage or transportation.

Palm wine is an alcoholic beverage that has existed for centuries and has important economic and socio-culture values in many tropical and sub-tropical countries. Lesser known than other types of wines, palm wine is made by spontaneous fermentation of palm sap by naturally occurring microbial communities. The palm sap ecosystem has unique microbial composition and diversity, which determines the composition of the eventual wine and is likely affected by geographical distinctiveness. While these features are well understood in grape and rice wine, these features have not been understood in palm wine. Here, we gather information of microbial communities and metabolite profiles from published studies, covering a wide range of methodologies and regions to better understand the causal links between the principal microbial species and major metabolites of palm wine. We assessed palm wine quality across production regions and local practices to provide general characteristics of palm wine and identify specific regional information. These will provide better understandings to the function of microbial communities and metabolite diversity, the contribution of regional variations and to ensure product quality in this unique, yet overlooked, fermented beverage.

Bacillus cereus is a common foodborne pathogen that frequently contaminates rice products and produces cereulide toxins, presenting a significant risk to food safety and human health. In contrast, Bacillus subtilis is a promising source of antimicrobial peptides (AMPs). In this research, a novel AMP named BCP4 (KGKTLLQ) was discovered through the fermentation of shrimp waste with B. subtilis, which speculated that BCP4 might be generated through enzymatic hydrolysis catalyzed by endogenous enzymes naturally present in shrimp waste. BCP4 demonstrated potent antibacterial activity against B. cereus with a minimum bactericidal concentration (MBC) of 62.5 μg/mL and bacterial time-kill of 3 h. BCP4 surpassed the bactericidal efficiency of nisin (500 μg/mL), a commonly used AMP of microbial origin. BCP4 operates by causing damage to the bacterial cell wall and membrane, which allows the contents of the cell to flow out. BCP4 also penetrates the cell membrane and binds with DNA, effectively sterilizing the bacteria. Meanwhile, treatment of BCP4 with mammalian red blood cells revealed that it was nonhemolytic. Furthermore, the growth of B. cereus in rice porridge was significantly inhibited by BCP4 at a concentration of 62.5 μg/mL. This study provides a theoretical basis for using BCP4 to control B. cereus contamination.

Industries that produce or use fruit-based products have faced several spoilage events, resulting in economic losses caused by product recalls and loss of consumer confidence. Some of these events correlate to the presence of Alicyclobacillus (ACB) in food products since they can produce off-flavours and odours in the final products. Guaiacol (2-methoxyphenol) and halophenols (2,6-dichlorophenol and 2,6-dibromophenol) have been widely explored as the primary culprits of off-flavour spoilage by ACB. However, different compounds might be correlated with these spoilage events. In this work, volatile metabolites produced by distinct ACB species (Alicyclobacillus acidoterrestris, Alicyclobacillus acidocaldarius, and Alicyclobacillus cycloheptanicus) in laboratory medium and fruit juices were identified by HS-SPME-GC-MS and investigated as potential spoilage-related compounds. Isobutyric acid (2-methylpropanoic acid) and isovaleric acid (3-methylbutanoic acid) were revealed to be produced by all three ACB species at concentrations that surpass the odour threshold. These cheesy, sweaty, and sour compounds were responsible for dissonant odours in peach, orange, and tomato juice, harming fruit-based products' quality. More importantly, this work suggests that ACB species previously identified as non-spoilage bacteria, based on a lack of ability to produce guaiacol and halophenols, can also threaten the juice, beverage, and dairy industries. As such, identification methods currently used in industries for ACB control in final products should be revised.

Salmonella is one of the most common bacterial foodborne pathogens and is frequently found as a contaminant of raw egg-based foods. Food safety regulations recommend the use of food acids to mitigate the risk of Salmonella persistence in raw egg-based foods. Salmonella, however, can become tolerant to acidic environments and it is not known how this can affect bacterial persistence in food. This study investigated whether acid-tolerant strains of Salmonella persisted longer in mayonnaise compared with sensitive strains. Isolates of S. typhimurium, S. infantis, S. enteritidis, and S.hessarek were used in this project. Acid-tolerant Salmonella strains were generated using a three-day step-down method where pH was decreased every 24 h from pH 7 to pH 5. Growth curves were determined for both acid-sensitive and acid-tolerant strains. Time-kill experiments were conducted to compare the survivability of acid-sensitive and acid-tolerant Salmonella serotypes in mayonnaise stored at either 5 °C or 25 °C for 72 h. Salmonella exhibited an extended lag phase with increased acid concentration, and acid-tolerant strains recovered faster in media compared with acid-sensitive strains. Elevated biofilm formation was found in acid-habituated strains compared to sensitive strains, and this varied between serotypes. The culturability of Salmonella in mayonnaise stored at 5 °C declined slower than when stored at 25 °C. Acid-tolerant strains persisted longer in mayonnaise and there was a statistically significant difference in culturability (P < 0.05). In conclusion, the current safe food recommendations to control Salmonella in raw egg-based foods are not effective in eliminating it.

This study aimed to evaluate the behavior of Pseudomonas aeruginosa (PSA) in natural mineral water sourced from three different extraction wells and stored at various temperatures (10, 12, 20, 23, and 30 °C) to calculate the kinetic growth parameters of this microorganism through predictive modeling. The physicochemical characterization of waters was also evaluated at the time of collection, and included the analysis of 40 different minerals, and quality parameters such as pH, conductivity, oxidation-reduction potential (ORP), total dissolved solids (TDS), salinity (PSU), and temperature (T). PSA survived in raw mineral water incubated at 12, 20, 23, and 30 °C; however, no growth was observed at 10 °C. Growth curves started with an initial population of ∼ 2.5-3 log CFU/mL, and final PSA populations ranged from 3.5 to 4.9 log CFU/mL. The maximum specific growth rate (μ_max) at 30 °C varied among the wells, with Well P-07 showing the highest growth rate (0.2 h^-1), followed by Well P-08 (0.195 h^-1) and well P-01 (0.133 h^-1). At 12 °C, well P-01 exhibited the highest growth rate (μ_max = 0.22 h^-1), indicating a influence of mineral composition in the growth of PSA. The lag time (λ) also varied, with minimum values of 2.4 ± 0.1 h at 30 °C and maximum values of 41.6 ± 0.2 h at 12 °C. From these primary estimated parameters, it was possible to obtain five robust secondary models to describe the influence of temperature on the maximum growth rates and lag phase of PSA in the well. The estimated PSA growth parameters at 20 and 23 °C were subjected to a hierarchical cluster analysis and correlation plots to verify the influence of the physicochemical composition of the waters on the PSA behavior at each well's specific annual average temperature. This analysis confirmed a positive relationship (p < 0.05) between the presence of minerals (Ca, Fe, Sr, Mn, Na) and ions (SO₄^-3, Cl^-) and the PSA lag phase time. These results underscore the need for tailored water quality management strategies that consider chemical composition and temperature to address specific microbial contamination risks.

Staphylococcus aureus is a major cause of gastroenteritis, commonly associated with the consumption of food contaminated at any stage of the food supply chain. Sous vide seafood has the potential to be a vehicle for the spread of S. aureus and enterotoxins due to low temperature cooking. This study aimed to investigate the antimicrobial activity of quince leaf extracts and the impact on the survival of S. aureus during sous vide process at frequently utilized temperatures. The results of the disk diffusion assay demonstrated the antibacterial efficiencies of extracts obtained using ethanol and methanol, with inhibition zone diameters of 9.8 and 11.2 mm, respectively. In contrast, aqueous extract had no effect on the bacteria. Since methanolic extract was the most effective one, phenolic profile was analyzed. Quercetin-3-O-rutinoside was the major compound (43.0 %) followed by 3-O-caffeoylquinic acid (21.8 %). Quince leaf methanolic extract (QM) was added to seabream to examine the thermal inactivation kinetics of S. aureus. The D values of QM-treated group ranged from 9.80 and 0.39 min, while those of the untreated samples varied between 11.36 and 0.51 min at 56-62 °C. The addition of QM to sous vide seabream significantly reduced the time needed to inactivate S. aureus. The z values of S. aureus in QM and untreated groups were 4.19 and 4.32 °C, respectively. Beneficial results could be achieved by adding quince extracts thereby; reducing S. aureus in sous vide fish and enhancing food safety. Developing efficient thermal processing techniques and combining additional hurdles are promising strategies for accomplishing pathogen inhibition.