Antimicrobial packaging based on ɛ-polylysine bioactive film for the control of mycotoxigenic fungi in vitro and in bread

ɛ-Poly-l-lysine (ɛ-PL) is a cationic peptide with a broad-spectrum antimicrobial activity. This study investigates the use of ɛ-PL as natural antimicrobial to inhibit fungal growth and to reduce aflatoxins (AFs) production. Antifungal activity of starch biofilms with different concentrations of ɛ-Poly-l-lysine (ɛ-PL) was determined in solid medium against Aspergillus parasiticus (AFs producer) and Penicillium expansum. Then, biofilms were tested as antimicrobial devices for the preservation of bread loaf inoculated with A. parasiticus CECT 2681 and P. expansum CECT 2278. Shelf life and AFs content were examined. Biofilms with concentrations of ɛ-PL less than 1.6 mg/cm2 showed no fungal growth inhibition in solid medium, while the antifungal activity of the films with greater than 1.6 mg/cm2 of ɛ-PL was dose dependent. The shelf life of bread inoculated with A. parasiticus was increased by 1 day with the use of films containing 1.6-6.5 mg ɛ-PL/cm2, while shelf life of bread tainted with P. expansum was increased by 3 day with 6.5 mg ɛ-PL/cm2. AFs production was greatly inhibited by ɛ-PL biofilms (93-100%). Thus, ɛ-PL biofilms could be potentially used as antimicrobial device during bread storage as a natural alternative to the synthetic preservatives.

Practical applications

Ɛ-Polylysin is a natural substance from microbial metabolism. Polylysine has a function to prevent a microbe from proliferating by ionic adsorption in the microbe. ɛ-polylysine has a wide antibacterial spectrum and has an obvious lethal effect on Gram-positive and Gram-negative bacteria, yeast, mold, viruses, etc. It has a good antibacterial effect on the Gram-negative bacteria E. coli and Salmonellae, which are difficult to control with other natural preservatives. ɛ-Polylysine has already been used generally as a food additive in Japan, Korea and other part of world. In the United States, FDA has recognized the polylysine as a GRAS material. Considered the positive results obtained in the study, this compound could be used for the production of antimicrobial biofilms, applied as separator slices in the loaf bread production, to prevent the growth of the mycotoxigenic fungi A. parasiticus and P. expansum, contributing to reduce the use of the synthetically preservatives in bakery industry and also of the negative impact that these compounds could generate on the health of the end users.

Occurrence, toxicity, bioaccessibility and mitigation strategies of beauvericin, a minor Fusarium mycotoxin

Emerging Fusarium mycotoxins include the toxic secondary metabolites fusaproliferin, enniatins, beauvericin (BEA), and moniliform. BEA is produced by some entomo- and phytopathogenic Fusarium species and occurs naturally on corn and corn-based foods and feeds infected by Fusarium spp. BEA has shown various biological activities (antibacterial, antifungal, and insecticidal) and possesses toxic activity, including the induction of apoptosis, increase cytoplasmic calcium concentration and lead to DNA fragmentation in mammalian cell lines. Cereals food processing has an important effect on mycotoxin stability, leading to less-contaminated food compared to the raw materials. Different industrial processes have shown to be effective practices to reduce BEA contents due to thermal food processing applied, such as cooking, boiling, baking, frying, roasting and pasteurization. Some studies demonstrated the capacity of lactic acid bacteria to reduce the presence of the BEA in model solution and in food chain through fermentation processes, modifying this mycotoxin in a less toxic derivate. Prebiotic and probiotic ingredient can modulate the bioaccessibility of BEA reducing the risk of intake of this minor Fusarium mycotoxin. This review summarizes the existing data on occurrence, toxicity and especially on BEA reduction strategies in food and feed such as chemical reduction, biocontrol and food processing.

Reaction of zearalenone and α-zearalenol with allyl isothiocyanate, characterization of reaction products, their bioaccessibility and bioavailability in vitro

This study investigates the reduction of zearalenone (ZEA) and α-zearalenol (α-ZOL) on a solution model using allyl isothiocyanate (AITC) and also determines the bioaccessibility and bioavailability of the reaction products isolated and identified by MS-LIT. Mycotoxin reductions were dose-dependent, and ZEA levels decreased more than α-ZOL, ranging from 0.2 to 96.9% and 0 to 89.5% respectively, with no difference (p⩽0.05) between pH 4 and 7. Overall, simulated gastric bioaccessibility was higher than duodenal bioaccessibility for both mycotoxins and mycotoxin-AITC conjugates, with duodenal fractions representing ⩾63.5% of the original concentration. Simulated bioavailability of reaction products (α-ZOL/ZEA-AITC) were lower than 42.13%, but significantly higher than the original mycotoxins. The cytotoxicity of α-ZOL and ZEA in Caco-2/TC7 cells was also evaluated, with toxic effects observed at higher levels than 75μM. Further studies should be performed to evaluate the toxicity and estrogenic effect of α-ZOL/ZEA-AITC.

The amount and proteolytic content of vesicles shed by human cancer cell lines correlates with their in vitro invasiveness

Cancer cells are known to shed extracellular membrane vesicles both in vitro and in vivo. To analyse their possible involvement in the metastatic behaviour of tumours, we measured the Matrigel invasion capability and amounts of vesicles shed by four human tumour cell lines (8701-BC, MCF-7, MDA-MB-231 and HT-1080), and by MCF-10A, an immortalised human breast cell line. The proteolytic activity content of vesicles was analysed by gelatin and casein zymographies. While MCF-10A cells do not release a measurable amount of vesicles, all tumour lines analysed, when cultured in presence of serum, shed vesicles rich in MMP-9. Other vesicle-associated proteinases include MMP-2 and uPA. Amounts and proteolytic activities of shed vesicles correlate with the in vitro invasiveness of cells. Since vesicles appear to promote the proteolytic cascade required for the localised degradation of the extracellular matrix, their shedding from cancer cells might represent an important feature of tumour progression.