Plant Bioactive Compounds as an Intrinsic and Sustainable Tool to Enhance the Microbial Safety of Crops

Escherichia coli O157:H7 multiplication in the latex of diverse lettuce genotypes is negatively correlated with plant peroxidase activity

Lettuce (Lactuca spp.) is one of few edible plant species that produce latex. During lettuce harvest, latex leaks from ruptured laticifers onto the cut stem and adheres to other lettuce heads, harvesting tools, and packaging. Little is known about the colonization of lettuce latex by Shiga toxin-producing E. coli O157:H7 (EcO157), the main causal agent of outbreaks linked to lettuce. We screened 14 lettuce genotypes, including wild lettuce and commercial morphological types, for EcO157 multiplication in their latex-coated cut stems. Change in EcO157 density after its inoculation into the latex of these genotypes differed significantly and ranged from a 1.7× decline to a 3.6× increase over 6 h at 25 °C. EcO157 density increased in all genotypes except one, a romaine lettuce breeding line that caused decline of the pathogen. Latex biochemical properties, such as concentration of sucrose, glucose, fructose, phenolic compounds and H2O2, and peroxidase (POD) activity, were quantified in all genotypes. These traits varied significantly among genotypes, but only POD activity correlated significantly with the change of EcO157 density in the latex (r = -0.553). Total phenolics and H2O2 concentrations were also negatively and significantly correlated with each other (r = -0.608). The inhibitory effect of POD on EcO157 multiplication in lettuce latex and the identification of a genotype that causes decline of the pathogen in its latex may serve as new phenotypic and genotypic tools to control microbial contamination of lettuce at harvest. Their integration in lettuce breeding programs may enhance the microbial safety of lettuce.

Association of Escherichia coli O157:H7 Density Change with Hydrogen Peroxide but Not Carbohydrate Concentration in the Leaf Content of Different Lettuce Types and Spinach

Leafy greens injuries occur from farm to table, causing leakage of cellular contents that promote the multiplication of foodborne pathogens and impose oxidative stress. Fresh beverages made from blended uncooked fruit and vegetables have become a popular food. The effect of cellular contents of different leafy greens on the multiplication of the important pathogen Escherichia coli O157:H7 (EcO157) under temperature abuse was investigated. Leafy greens consisted of spinach and different lettuce types (romaine, iceberg, butterhead, green leaf, and red leaf). Fructose, glucose, and sucrose concentrations in the leaves were quantified by HPLC. H2O2 concentration was measured via a peroxidase-based assay. Young leaves of iceberg, romaine, and green leaf lettuce held significantly greater total amounts of the three carbohydrates than middle-aged leaves. Except for iceberg and red leaf lettuce, all middle-aged leaves contained greater H2O2 than young leaves. EcO157 density change in leaf contents over 5 h incubation related neither to individual nor total carbohydrate concentration but was negatively associated with H2O2 concentration (regression analysis; p < 0.05). Given the common use of antioxidants to maintain the organoleptic aspects of homogenized produce beverages and certain fresh-cut produce, the antimicrobial effect of reactive oxygen species may be important to preserve in ensuring their microbial safety.

Nanocellulose: A novel pathway to sustainable agriculture, environmental protection, and circular bioeconomy

Nanocellulose, obtained from natural cellulose, has attracted considerable interest for its distinctive properties and wide-ranging potential applications. Studies suggest that nanocellulose improves the thermal, mechanical, and barrier properties of conventional cellulose. This review investigates the production, properties, approach, and application of nanocellulose from various sources in agriculture. The main role play of cellulose-nanocomposite is discussed as a seed coating agent to improve seed dispersal, germination, protection against fungi and insects, plant growth promoter, adsorption of targeted pollutants, providing water and nutrient retention, and other advantages. As a nobility, we included all mechanical, chemical, and static culture approaches to the production procedure of nanocellulose and its application as a nanocarrier in soil, including the unique properties of nanocellulose, such as its high surface area, inherent hydrophilicity, and ease of surface modification. Here, methods such as melt compounding, solution casting, and in situ polymerization were evaluated to incorporate nanoparticles into cellulose materials and produce nanocellulose and cellulose-nanocomposites with improved strength, stability, water resistance, and reduced gas permeability. The commercialization faces challenges such as high production costs, scalability issues, and the need for more research on environmental impacts and plant interactions. Despite these hurdles, this field is promising, with ongoing advancements likely to yield new and improved agricultural materials. This review thoroughly examines the innovative application of nanocellulose in slow and controlled-release fertilizers and pesticides, to transform nutrient management, boost crop productivity, and minimize the environmental impact.

A greener side of health care: Revisiting phytomedicine against the human fungal pathogen Malassezia

Malassezia species are commensal fungi residing on the skin and in the gut of humans and animals. Yet, under certain conditions, they become opportunistic pathogens leading to various clinical conditions including dermatological disorders. The emergence of drug resistance and adverse effects associated with conventional antifungal agents has propelled the search for alternative treatments, among which phytomedicine stands out prominently. Phytochemicals, including phenolic acids, flavonoids, and terpenoids, demonstrate potential antifungal activity against Malassezia by inhibiting its growth, adhesion, and biofilm formation. Furthermore, the multifaceted therapeutic properties of phytomedicine (including anti-fungal and, antioxidant properties) contribute to its efficacy in alleviating symptoms associated with Malassezia infections. Despite these promising prospects, several challenges hinder the widespread adoption of phytomedicine in clinical practice mostly since the mechanistic studies and controlled experiments to prove efficacy have not been done. Issues include standardization of herbal extracts, variable bioavailability, and limited clinical evidence. Hence, proper regulatory constraints necessitate comprehensive research endeavors and regulatory frameworks to harness the full therapeutic potential of phytomedicine. In conclusion, while phytomedicine holds immense promise as an alternative or adjunctive therapy against Malassezia, addressing these challenges is imperative to optimize its efficacy and ensure its integration into mainstream medical care. In this review we provide an update on the potential phytomedicines in combating Malassezia-related ailments, emphasizing its diverse chemical constituents and mechanisms of action.

Stabilization of Picea abies Spruce Bark Extracts within Ice-Templated Porous Dextran Hydrogels

Porous hydrogels have brought more advantages than conventional hydrogels when used as chromatographic materials, controlled release vehicles for drugs and proteins, matrices for immobilization or separation of molecules and cells, or as scaffolds in tissue engineering. Polysaccharide-based porous hydrogels, in particular, can address challenges related to bioavailability, solubility, stability, and targeted delivery of natural antioxidant compounds. Their porous structure enables the facile encapsulation and controlled release of these compounds, enhancing their therapeutic effectiveness. In this context, in the present study, the cryogelation technique has been adopted to prepare novel dextran (Dx)-based porous hydrogels embedding polyphenol-rich natural extract from Picea abies spruce bark (SBE). The entrapment of the SBE within the Dx network was proved by FTIR, SEM, and energy-dispersive X-ray spectroscopy (EDX). SEM analysis showed that entrapment of SBE resulted in denser cryogels with smaller and more uniform pores. Swelling kinetics confirmed that higher concentrations of Dx, EGDGE, and SBE reduced water uptake. The release studies demonstrated the effective stabilization of SBE in the Dx-based cryogels, with minimal release irrespective of the approach selected for SBE incorporation, i.e., during synthesis (~3-4%) or post-synthesis (~15-16%). In addition, the encapsulation of SBE within the Dx network endowed the hydrogels with remarkable antioxidant and antimicrobial properties. These porous biomaterials could have broad applications in areas such as biomedical engineering, food preservation, and environmental protection, where stability, efficacy, and safety are paramount.

Characterization of antifungal properties of avocado leaves and majagua flowers extracts and their potential application to control Alternaria alternata

Plant extracts are used as an alternative to a wide range of foods against different types of fungal pathogens. In the present study, the extracts of avocado leaves (Persea americana) and majagua flowers (Talipariti elatum) were tested according to their antifungal activity against different fungi. The most promising extracts were those of majagua flowers that were applied lyophilized and in aqueous extract, being very effective against Alternaria alternata and reaching a 50 % in vitro reduction. Antifungal properties were also evaluated during infection of apples by A. alternata. A decrease in infection progression was confirmed with up to a 30 % reduction in disease incidence and a 20 % reduction in disease severity. Majagua extracts were also tested combined with edible pectin coatings, greatly increasing their effectiveness up 60 % reduction. Thus, extracts of majagua could provide a feasible alternative to control fungal pathogens during postharvest.

Natural Antimicrobials: A Reservoir to Contrast Listeria monocytogenes

Natural environments possess a reservoir of compounds exerting antimicrobial activity that are forms of defence for some organisms against others. Recently, they have become more and more attractive in the food sector due to the increasing demand for natural compounds that have the capacity to protect food from pathogenic microorganisms. Among foodborne pathogens, Listeria monocytogenes can contaminate food during production, distribution, or storage, and its presence is especially detected in fresh, raw food and ready-to-eat products. The interest in this microorganism is related to listeriosis, a severe disease with a high mortality rate that can occur after its ingestion. Starting from this premise, the present review aims to investigate plant extract and fermented plant matrices, as well as the compounds or mixtures of compounds produced during microbial fermentation processes that have anti-listeria activity.

Human Pathogens in Primary Production Systems

Human pathogenic micro-organisms can contaminate plants [...]

Natural variation and drought-induced differences in metabolite profiles of red oak-leaf and Romaine lettuce play a role in modulating the interaction with Salmonella enterica

Nutrients on produce surfaces are vital for successful enteric pathogen colonisation. In this study, we investigated natural variation in metabolite profiles of Romaine 'Parris Island Cos' and red oak-leaf lettuce 'Mascara' under regular and restricted watering conditions. We also investigated the impact of plant drought stress on the Salmonella - lettuce association. Salmonella Newport and Typhimurium were able to persist at higher levels on regularly watered Romaine than red oak-leaf lettuce. Drought treatment to lettuce impaired epiphytic Salmonella association, with S. Newport and Typhimurium being differentially affected. A higher log reduction of both serotypes was measured on drought-subjected red oak-leaf lettuce plants than controls, but S. Typhimurium was unaffected on water deficit-treated Romaine lettuce (p < 0.05). To assess Salmonella interaction with leaf surface metabolites, leaf washes collected from both cultivars were inoculated and found to be able to support S. Newport growth, with higher levels of Salmonella retrieved from Romaine washes (p < 0.05). The lag phase of S. Newport in washes from water restricted red oak-leaf lettuce was prolonged in relation to regularly-watered controls (p < 0.05). Untargeted plant metabolite profiling using electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) revealed natural variation between Romaine and red oak-leaf lettuce profiles for leaf tissue and leaf washes. Metabolite profile shifts were detected in both lettuce types in response to drought stress, but more unique peaks were detected in red oak-leaf than Romaine lettuce after drought treatment. Variation between the two cultivars was in part attributed to naturally higher levels of flavonoids and anthocyanins in red oak-leaf lettuce compared to Romaine. Moreover, red oak-leaf, but not Romaine lettuce, responded to drought by inducing the accumulation of proline, phenolics, flavonoids and anthocyanins. Drought stress, therefore, enhanced the functional food properties of red oak-leaf lettuce. Salmonella growth dynamics in lettuce leaf washes suggested that natural variation and drought-induced changes in metabolite profiles in lettuce could partly explain the differential susceptibility of various lettuce types to Salmonella, although the primary or secondary metabolites mediating this effect remain unknown. Regulated mild water stress should be investigated as an approach to lower Salmonella contamination risk in suitable lettuce cultivars, while simultaneously boosting the health beneficial quality of lettuce.

Electrospun nanofibers with antibacterial properties for wound dressings

The antibacterial nanofibers have been proposed as an interesting material for wound healing management, since the majority of traditional wound dressings exhibit issues and complications such as infection, pain, discomfort, and poor adhesive proprieties. It allows the organism's passage through the dressing and delay the wound healing progression. Electrospun nanofibers have been intensively investigated for wound dressings in tissue engineering applications due to their distinctive features and structural similarities to the extracellular matrix including the various available methods to load the antibacterial compounds onto the nanofiber webs. To construct an effective electrospun wound dressing, various efforts have been made to design different strategies to develop advanced polymers, such as employing synthetic and/or natural materials, modifying fiber orientation, and incorporating chemicals and metallic nanoparticles (NPs) as intriguing materials for antibacterial bandages. Thus, this review summarizes the relevant recent studies on the production of electrospun antibacterial nanofibers from a wide variety of polymers used in biomedical applications for wound dressings.

Performance of Thermoplastic Extrusion, Germination, Fermentation, and Hydrolysis Techniques on Phenolic Compounds in Cereals and Pseudocereals

Bioactive compounds, such as phenolic compounds, are phytochemicals found in significant amounts in cereals and pseudocereals and are usually evaluated by spectrophotometric (UV-VIS), HPLC, and LC-MS techniques. However, their bioavailability in grains is quite limited. This restriction on bioavailability and bioaccessibility occurs because they are in conjugated polymeric forms. Additionally, they can be linked through chemical esterification and etherification to macro components. Techniques such as thermoplastic extrusion, germination, fermentation, and hydrolysis have been widely studied to release phenolic compounds in favor of their bioavailability and bioaccessibility, minimizing the loss of these thermosensitive components during processing. The increased availability of phenolic compounds increases the antioxidant capacity and favor their documented health promoting.