Our research indicated that sublethal chlorine stress, at a concentration of 350 ppm total chlorine, stimulated the expression of biofilm genes (csgD, agfA, adrA, and bapA), as well as quorum-sensing genes (sdiA and luxS), in the planktonic cells of Salmonella Enteritidis. A heightened expression of these genes signified that chlorine stress prompted the beginning of the biofilm formation procedure in *S. Enteritidis*. The initial attachment assay's results corroborated this observation. After 48 hours of incubation at 37 degrees Celsius, a statistically significant increase in the number of chlorine-stressed biofilm cells was evident, compared to non-stressed biofilm cells. In S. Enteritidis ATCC 13076 and S. Enteritidis KL19, the count of chlorine-stressed biofilm cells reached 693,048 and 749,057 log CFU/cm2, respectively, whereas the number of non-stressed biofilm cells amounted to 512,039 and 563,051 log CFU/cm2, respectively. These findings were substantiated by quantifying the major biofilm constituents: eDNA, protein, and carbohydrate. In 48-hour biofilms, the quantity of these components was greater when cells were initially stressed by sublethal chlorine. Nevertheless, the biofilm and quorum sensing gene upregulation was not evident in 48-hour biofilm cells, suggesting the chlorine stress effect was lost in subsequent Salmonella generations. Sublethal concentrations of chlorine, according to these results, can cultivate the biofilm-forming properties of S. Enteritidis bacteria.
Among the prevalent spore-forming microorganisms in heat-treated foods are Anoxybacillus flavithermus and Bacillus licheniformis. To date, a systematic investigation into the growth kinetics of A. flavithermus or B. licheniformis has not, to our knowledge, been undertaken in a published context. The present research explored the growth kinetics of A. flavithermus and B. licheniformis in broth solutions, investigating their behavior across a range of temperatures and pH values. Cardinal models were applied to evaluate the effect of the above-cited factors regarding growth rates. Regarding the estimated values for A. flavithermus, the cardinal parameters Tmin, Topt, and Tmax were 2870 ± 026, 6123 ± 016, and 7152 ± 032 °C, respectively. Simultaneously, the pH values were 552 ± 001 and 573 ± 001. For B. licheniformis, the estimated cardinal parameters were 1168 ± 003, 4805 ± 015, and 5714 ± 001 °C for Tmin, Topt, and Tmax, with the corresponding pH values being 471 ± 001 and 5670 ± 008. To adapt the models for this pea-based beverage, the growth patterns of the spoilers were scrutinized at both 62°C and 49°C. The adjusted models, when tested under static and dynamic conditions, displayed robust performance. 857% and 974% of predicted A. flavithermus and B. licheniformis populations, respectively, fell within the -10% to +10% relative error (RE) range. The developed models offer useful tools for the assessment of spoilage potential in heat-processed foods, including innovative plant-based milk alternatives.
Meat spoilage, under high-oxygen modified atmosphere packaging (HiOx-MAP), is frequently caused by the dominance of Pseudomonas fragi. A study was undertaken to analyze the impact of carbon dioxide on the development of *P. fragi* and subsequent spoilage of the HiOx-MAP beef product. P. fragi T1, the strain with the highest spoilage capacity among the isolates, was used to cultivate minced beef, which was then held at 4°C for 14 days in either a CO2-enriched HiOx-MAP (TMAP; 50% O2/40% CO2/10% N2) or a non-CO2 HiOx-MAP (CMAP; 50% O2/50% N2) environment. TMAP, in contrast to CMAP, kept sufficient oxygen concentrations, which led to enhanced a* values and greater meat color stability in the beef, resulting from a smaller P. fragi population from day one (P < 0.05). 5-Fluorouracil molecular weight TMAP samples demonstrated a decrease in lipase activity, statistically significant (P<0.05), within 14 days, and a comparable decrease in protease activity (P<0.05), observed within 6 days, in comparison to CMAP samples. Storage of CMAP beef experienced a delayed increase in both pH and total volatile basic nitrogen, an effect attributed to TMAP. 5-Fluorouracil molecular weight While TMAP fostered a more pronounced lipid oxidation, as indicated by heightened levels of hexanal and 23-octanedione than CMAP (P < 0.05), TMAP beef maintained an acceptable olfactory quality owing to carbon dioxide's suppression of microbial-generated 23-butanedione and ethyl 2-butenoate. This research presented a complete examination of CO2's antibacterial mechanisms for P. fragi in the presence of HiOx-MAP beef.
In the wine industry, Brettanomyces bruxellensis stands out as the most damaging spoilage yeast, primarily due to its adverse effect on wine's organoleptic properties. Repeated wine contamination in cellars over years highlights the persistence of certain properties, capable of enduring environmental conditions and enabling survival through bioadhesion. The adhesion of the materials to stainless steel, including their surface properties, morphology, and behavior in synthetic solutions and wine, were investigated in this research. A substantial number of strains, exceeding fifty, representing the full genetic spectrum of the species, were taken into account. By employing microscopy, scientists could observe a remarkable range of cellular forms, notably the presence of pseudohyphae in some genetically distinct cell populations. The cell surface's physical and chemical attributes are revealed through analysis to show diverse behaviors amongst the strains; most exhibit a negative surface charge and hydrophilic character, contrasting with the Beer 1 genetic group that exhibits hydrophobic behavior. Bioadhesion capabilities were demonstrated by every strain on stainless steel samples, becoming apparent within three hours. The concentration of cells adhering varied significantly, from a low of 22 x 10^2 to a high of 76 x 10^6 cells per square centimeter. Our investigation culminates in a demonstration of significant variation in bioadhesion characteristics, the foundational process in biofilm creation, demonstrating a strong dependence on the genetic classification showing the most pronounced bioadhesion potential, particularly evident in the beer group.
Research into and practical application of Torulaspora delbrueckii for the alcoholic fermentation of grape must is growing within the wine industry. Beyond the improved sensory characteristics of wines, the collaborative effect of this yeast species and the lactic acid bacterium Oenococcus oeni is a fascinating subject for scientific inquiry. Sixty-strain combinations of Saccharomyces cerevisiae (Sc), Torulaspora delbrueckii (Td) and Oenococcus oeni (Oo) were investigated. Three Sc strains, four Td strains were utilized in sequential alcoholic fermentation (AF). Four Oo strains were assessed in malolactic fermentation (MLF). Our objective was to characterize the positive or negative relationships between these strains, with the ultimate aim of identifying the optimal combination for enhanced MLF outcomes. Additionally, a manufactured synthetic grape must has been produced, allowing for successful AF implementation and subsequent MLF. The Sc-K1 strain's suitability for MLF is compromised under these conditions, requiring a preliminary inoculation with Td-Prelude, Td-Viniferm, or Td-Zymaflore, invariably with the Oo-VP41. The results from the trials indicate that a sequence involving AF, Td-Prelude, and either Sc-QA23 or Sc-CLOS, followed by MLF and Oo-VP41, demonstrably demonstrated the positive effect of T. delbrueckii compared to the control of Sc alone, as illustrated by a reduction in the time required for L-malic acid consumption. Finally, the results demonstrate the crucial role of strain selection and the proper balance between yeast and lactic acid bacteria in winemaking. The study's findings also indicate a positive influence on MLF stemming from particular T. delbrueckii strains.
A major food safety concern arises from the acid tolerance response (ATR) developed in Escherichia coli O157H7 (E. coli O157H7) when exposed to low pH in beef during processing. An investigation into the development and molecular mechanisms of the tolerance response of E. coli O157H7 in a simulated beef processing environment involved evaluating the resistance of a wild-type (WT) strain and its corresponding phoP mutant to acid, heat, and osmotic pressure. Strains were pre-conditioned under different pH values (5.4 and 7.0), temperature parameters (37°C and 10°C), and diverse culture media types (meat extract and Luria-Bertani broth). Besides, the expression of genes tied to stress response and virulence was also evaluated across wild-type and phoP strains under the specified experimental conditions. Pre-acid adaptation boosted the resistance of E. coli O157H7 to acid and heat conditions, but its resistance to osmotic pressure experienced a reduction. Besides, acid adaptation within a meat extract simulating a slaughterhouse setting increased the ATR, but prior adaptation at 10 degrees Celsius reduced the ATR. The synergistic action of mildly acidic conditions (pH 5.4) and the PhoP/PhoQ two-component system (TCS) was observed to improve the acid and heat tolerance of E. coli O157H7. Elevated expression of genes pertaining to arginine and lysine metabolism, heat shock proteins, and invasiveness mechanisms was observed, implying that the PhoP/PhoQ two-component system is responsible for the acid resistance and cross-protection under mildly acidic conditions. Reduced relative expression of the stx1 and stx2 genes, identified as crucial pathogenic factors, was observed following both acid adaptation and phoP gene inactivation. In beef processing, the current findings indicate a possibility of ATR involving E. coli O157H7. 5-Fluorouracil molecular weight Hence, the tolerance response's persistence in the subsequent processing conditions leads to an increased vulnerability in food safety. The current study furnishes a more complete framework for the successful implementation of hurdle technology in beef production.
Concerning climate change, a substantial reduction in malic acid concentration within grape berries is a hallmark of wine's chemical composition. To effectively control wine acidity, wine professionals need to discover pertinent physical and/or microbiological interventions.