Inhibitory effect of sweet whey fermented by Lactobacillus plantarum strains against fungal growth: A potential application as an antifungal agent

Utilization of Whey for Eco-Friendly Bio-Preservation of Mexican-Style Fresh Cheeses: Antimicrobial Activity of Lactobacillus casei 21/1 Cell-Free Supernatants (CFS)

Using whey, a by-product of the cheese-making process, is important for maximizing resource efficiency and promoting sustainable practices in the food industry. Reusing whey can help minimize environmental impact and produce bio-preservatives for foods with high bacterial loads, such as Mexican-style fresh cheeses. This research aims to evaluate the antimicrobial and physicochemical effect of CFS from Lactobacillus casei 21/1 produced in a conventional culture medium (MRS broth) and another medium using whey (WB medium) when applied in Mexican-style fresh cheese inoculated with several indicator bacteria (Escherichia coli, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, and Listeria monocytogenes). The CFSs (MRS or WB) were characterized for organic acids concentration, pH, and titratable acidity. By surface spreading, CFSs were tested on indicator bacteria inoculated in fresh cheese. Microbial counts were performed on inoculated cheeses during and after seven days of storage at 4 ± 1.0 °C. Moreover, pH and color were determined in cheeses with CFS treatment. Lactic and acetic acid were identified as the primary antimicrobial metabolites produced by the Lb. casei 21/1 fermentation in the food application. A longer storage time (7 days) led to significant reductions (p < 0.05) in the microbial population of the indicator bacteria inoculated in the cheese when it was treated with the CFSs (MRS or WB). S. enterica serovar Typhimurium was the most sensitive bacteria, decreasing 1.60 ± 0.04 log10 CFU/g with MRS-CFS, whereas WB-CFS reduced the microbial population of L. monocytogenes to 1.67 log10 CFU/g. E. coli and S. aureus were the most resistant at the end of storage. The cheese's pH with CFSs (MRS or WB) showed a significant reduction (p < 0.05) after CFS treatment, while the application of WB-CFS did not show greater differences in color (ΔE) compared with MRS-CFS. This study highlights the potential of CFS from Lb. casei 21/1 in the WB medium as an ecological bio-preservative for Mexican-style fresh cheese, aligning with the objectives of sustainable food production and guaranteeing food safety.

The functionalities and applications of whey/whey protein in fermented foods: a review

Whey, a major by-product of cheese production, is primarily composed of whey protein (WP). To mitigate environmental pollution, it is crucial to identify effective approaches for fully utilizing the functional components of whey or WP to produce high-value-added products. This review aims to illustrate the active substances with immunomodulatory, metabolic syndrome-regulating, antioxidant, antibacterial, and anti-inflammatory activities produced by whey or WP through fermentation processes, and summarizes the application and the effects of whey or WP on nutritional properties and health promotion in fermented foods. All these findings indicate that whey or WP can serve as a preservative, a source of high-protein dietary, and a source of physiologically active substance in the production of fermented foods. Therefore, expanding the use of whey or WP in fermented foods is of great importance for converting whey into value-added products, as well as reducing whey waste and potential contamination.

Assessment of the antifungal efficacy of whey fermentate alone or in combination with citrus extract to control Aspergillus flavus mold in semi-moist pet food for dogs

Semi-moist pet foods contain moisture levels ranging from 15 to 40%, making them ideal for mold growth and mycotoxin production. To control spoilage, synthetic mold inhibitors such as potassium sorbate have been used, but consumers prefer "natural" preservatives. Whey fermentate (WPF) is an efficient antifungal, but it requires large doses. Therefore, the objective of this study was to determine the antifungal effect of WPF alone or in combination with citrus extract oil (CEX) against Aspergillus flavus in semi-moist pet food. Nutritionally complete semi-moist pet foods were produced with WPF alone [0.25, 0.5, and 1.0% (w/w)] and in combination with CEX; 0.25% WPF+ 0.015% CEX, 0.25% WFP+ 0.15% CEX, 0.5% WPF+ 0.015% CEX, and 0.5% WFP+ 0.15% CEX (w/w). The negative control (NC) contained no antifungal additive and the positive control (PC) had potassium sorbate (0.1% w/w). The semi-moist pet food was thermally formed and was cut into 3 cm × 3 cm square pieces. Individual food pieces were inoculated with 0.1 mL of Aspergillus flavus (ATCC 204304) to achieve a final concentration of ~5.0 log CFU/piece. The inoculated pieces were individually incubated at 25°C. Fungal analysis was performed on day 3, 6, 9, 12, 15, 18, 21, 24, and 28 by surface plating on Potato Dextrose Agar (PDA) followed by incubation at 25°C for 72 h. The total log reductions were calculated by subtracting the initial inoculum from the final log counts on day 28. Higher log reductions of Aspergillus flavus (p < 0.05) were observed when WPF at 0.25 and 0.5% was combined with 0.15% CEX compared to when 0.015% CEX was used individually. All treatments were different from the NC (p < 0.05). Citrus extract at 0.15% potentiated the antifungal effect of WPF at 0.5% to give a similar log reduction (p > 0.05) to WPF at 1.0% in the food. In conclusion, CEX potentiated the antifungal efficacy and reduced the dose of WPF required to control Aspergillus flavus in semi-moist dog food.

Preparation of Sourdoughs Fermented with Isolated Lactic Acid Bacteria and Characterization of Their Antifungal Properties

Traditional sourdough is obtained using a mixture of flour and water stored at room temperature until acidification. Therefore, adding lactic acid bacteria (LAB) can improve the quality and safety of sourdough bread. Faced with this problem, four drying techniques-freeze-drying, spray-drying, low-temperature drying, and drying at low humidity-have been applied. Our goals were to isolate LAB strains with antifungal potential against Aspergillus and Penicillium fungi. The antifungal capacity was evaluated with agar diffusion, co-culture in overlay agar, and a microdilution susceptibility assay. In addition, the antifungal compounds generated in sourdough were analyzed. As a result, dried sourdoughs were prepared with Lactiplantibacillus plantarum TN10, Lactiplantibacillus plantarum TF2, Pediococcus pentosaceus TF8, Pediococcus acidilactici TE4, and Pediococcus pentosaceus TI6. The minimum fungicidal concentrations ranged from 25 g/L versus P. verrucosum and 100 g/L against A. flavus. A total of 27 volatile organic compounds were produced. Moreover, the lactic acid content reached 26 g/kg of dry product, and the phenyllactic concentration was significantly higher than the control. The P. pentosaceus TI6 exhibited a higher antifungal capacity in vitro and demonstrated a higher production of antifungal compounds compared to the other strains; therefore, further studies will evaluate the impact of this sourdough in bread manufacture.

Protective role of fermented whey and pumpkin extract against aflatoxin B1 and ochratoxin A toxicity in Jurkat T-cells

The beneficial effect of fermented whey and pumpkin extract rich in carotenoids was evaluated in Jurkat cells against aflatoxin B1 (AFB1) and ochratoxin A (OTA) cytotoxicity through a proteomic approach. The functional ingredients were added into mycotoxin contaminated bread formulation, which were digested in vitro in order to simulate human intestinal absorption. Cell cultures were exposed during 7 days to these mycotoxins dissolved in: (a) 0.1% organic solvent (DMSO), (b) an intestinal digest of bread with pumpkin individually (PID) and (c) an intestinal digest of bread with pumpkin mixed with fermented whey (PID+WF). Extracted proteins were subjected to reduction and alkylation and subsequently a tryptic digestion in order to be analysed by liquid chromatography coupled with quadrupole time of flight (LC/MS-Q-TOF). Results obtained highlighted the beneficial role of functional ingredients employed through the identification of proteins involved in several biological processes and metabolic pathways, mainly antioxidant activity, nucleosome assembly and secretory senescence phenotype. Among proteins involved in antioxidant activity, peroxiredoxin 1 and 2 stand out. Comparing the different conditions investigated, a remarkable change was observed in their expression, ranging from a repression using the standard (DMSO 0.1%), to an overexpression when treated with the functional ingredients. Similarly, after PID and PID+WF treatment, histones’ expression implicated in the metabolic pathway of nucleosome assembly, such as H2A, H2B, H2C, H3 and H4, was increased. Furthermore, the expression of protein cyclin A2, which downregulation is involved in limiting carcinogenic cells growth, was lower in presence of both functional ingredients. Based on these findings, functional ingredients can act as protectors against genomic stress caused by mycotoxins, preventing the loss of vital cell functions and paralysing the growth of carcinogenic cells.

Use of Mustard Extracts Fermented by Lactic Acid Bacteria to Mitigate the Production of Fumonisin B1 and B2 by Fusarium verticillioides in Corn Ears

Corn (Zea mays) is a worldwide crop subjected to infection by toxigenic fungi such as Fusarium verticillioides during the pre-harvest stage. Fusarium contamination can lead to the synthesis of highly toxic mycotoxins, such as Fumonisin B₁ (FB₁) and Fumonisin B₂ (FB₂), which compromises human and animal health. The work aimed to study the antifungal properties of fermented yellow and oriental mustard extracts using nine lactic acid bacteria (LAB) in vitro. Moreover, a chemical characterization of the main phenolic compounds and organic acids were carried out in the extracts. The results highlighted that the yellow mustard, fermented by Lactiplantibacillus plantarum strains, avoided the growth of Fusarium spp. in vitro, showing Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC) values, ranging from 7.8 to 15.6 g/L and 15.6 to 31.3 g/L, respectively. Then, the lyophilized yellow mustard fermented extract by L. plantarum TR71 was applied through spray-on corn ears contaminated with F. verticillioides to study the antimycotoxigenic activity. After 14 days of incubation, the control contained 14.71 mg/kg of FB₁, while the treatment reduced the content to 1.09 mg/kg (92.6% reduction). Moreover, no FB₂ was observed in the treated samples. The chemical characterization showed that lactic acid, 3-phenyllactic acid, and benzoic acid were the antifungal metabolites quantified in higher concentrations in the yellow mustard fermented extract with L. plantarum TR71. The results obtained confirmed the potential application of fermented mustard extracts as a solution to reduce the incidence of mycotoxins in corn ears.

Bioaccessibility and bioavailability of bioactive compounds from yellow mustard flour and milk whey fermented with lactic acid bacteria

Microbial fermentation with lactic acid bacteria (LAB) is a natural food biopreservation method. Yellow mustard and milk whey are optimum substrates for LAB fermentation. The aim of the present study was to evaluate the bioaccessibility and bioavailability of bioactive compounds from yellow mustard flour and milk whey both with and without LAB fermentation. All extracts were subjected to a simulated digestion process. Total polyphenols, DL-3-phenyllactic acid (PLA), lactic acid, and the antioxidant activity were determined in the studied matrices before and after simulated digestion. Yellow mustard flour was significantly richer in total polyphenols, whereas significantly higher concentrations of PLA and lactic acid were observed in milk whey. Similar antioxidant activity was determined in both ingredients being in all cases strongly reduced after in vitro digestion. Higher bioaccessibility was found for polyphenols and PLA in milk whey. Transepithelial transport of total polyphenols was higher in yellow mustard flour compared to milk whey, reaching bioavailability values between 3-7% and 1-2%, respectively. PLA transepithelial transport was only significant in both fermented matrices with bioavailability around 4-6%. Transepithelial transport of lactic acid reached values of 31-34% (bioavailability ∼ 22%) and 15-78% (bioavailability ∼ 3%) in milk whey and yellow mustard flour, respectively. LAB fermentation showed beneficial effects on enriching extracts with PLA, lactic acid, and antioxidant activity, as well as increasing bioaccessibility of these acids in yellow mustard flour and total polyphenol bioavailability in milk whey. Results pointed to yellow mustard flour and milk whey as natural preservative ingredients used in the food industry, especially when fermented with LAB.

Bio-Preservative Potential of Microorganisms Isolated from Red Grape against Food Contaminant Fungi

Fungal spoilage is one of the main reasons of economic losses in the food industry, especially in the wine sector. Consequently, the search for safer and new preservation techniques has gained importance in recent years. The objective of this study was to investigate the antifungal and anti-mycotoxigenic activity from 28 microorganisms (MO) isolated from red grape. The antifungal activity of a cell free supernatant of fermented medium by the isolated MO (CFS) was tested with the agar diffusion method and the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) assay. Additionally, different antifungal compounds from the CFS were identified and quantified (organic acids, phenolic compounds, and volatile organic compounds). Finally, the most active CFS were tested as red grape bio-preservative agents. Results evidenced that CFS fermented by the strain UTA 6 had the highest antifungal activity, above all isolates, and produced a wide pool of antifungal compounds. The use of UTA 6 CFS as bio-preservative agent showed a reduction of 0.4 and 0.6 log₁₀ spores per gram of fruit in grapes contaminated by A. flavus and B. cinerea, respectively. Moreover, UTA 6 CFS treatment reduced the occurrence of aflatoxin B₁ and fumonisin (B₂, B₃, and B₄) production in grapes contaminated by 28-100%.