Zsolt Zalán

Apple is a widely consumed fruit, but its quality can be compromised by mycotoxins such as patulin, produced mostly by Penicillium expansum , but also by the less-studied Aspergillus clavatus . This toxin poses a health risk, requiring effective control strategies. Biocontrol, particularly using yeasts, has gained attention as a promising method. In this study, we assessed the potential of different yeast strains to inhibit the growth of the patulin (PAT)-producing A. clavatus B9/6 and to remove patulin. While Saccharomyces cerevisiae , previously reported as an antagonist of P. expansum , showed no inhibitory effects on A. clavatus , all 13 Wickerhamomyces anomalus strains studied exhibited antifungal activity to varying degrees. Among them, strains 01499, 0961, 0170, and 01655 showed the strongest inhibition. Notably, W. anomalus 01499 not only inhibited fungal growth but also removed patulin, reducing the toxin by 71% within 24 h and achieving complete removal after 48 h under the tested experimental conditions (10 ppm patulin in apple juice). In vivo assays in apples showed that pre-inoculation with W. anomalus 01499 strongly suppressed fungal infection, whereas delayed application resulted in more severe symptoms, emphasizing the importance of early intervention. Mechanistic studies revealed that patulin removal occurred primarily through cell wall binding (11%) and intracellular components (including enzymes) (33%), while no contribution from extracellular enzyme activity was detected. These results suggest that W. anomalus 01499 is a promising candidate for the biocontrol of A. clavatus and for reducing patulin contamination in apples. This study provides further evidence supporting the potential role of W. anomalus in patulin removal and fungal biocontrol.

Sustainability is becoming increasingly important in the world we live in, because of the rapid global population growth and climate change (drought, extreme temperature fluctuations). People in developing countries need more sustainable protein sources instead of the traditional, less sustainable meat, fish, egg, and dairy products. Alternative sources (plant-based, such as grains (wheat, rice sorghum), seeds (chia, hemp), nuts (almond, walnut), pulses (beans, lentil, pea, lupins), and leaves (duckweed), as well as mycoproteins, microalgae, and insects) can compensate for the increased demand for animal protein. In this context, our attention has been specifically focused on duckweed—which is the third most important aquatic plant after the microalgae Chlorella and Spirulina—to explore its potential for use in a variety of areas, particularly in the food industry. Duckweed has special properties: It is one of the fastest-growing plants in the world (in freshwater), multiplying its mass in two days, so it can cover a water surface quickly even in filtered sunlight (doubling its biomass in 96 hours). During this time, it converts a lot of carbon dioxide into oxygen. It is sustainable, environmentally friendly (without any pesticides), and fast growing; can be grown in indoor vertical farms and aquaculture, so it does not require land; is easy to harvest; and has a good specific protein yield. Duckweed belongs to the family Araceae, subfamily Lemnoideae, and has five genera (Lemna, Spirodela, Wolffia, Wolffiella, Landolita) containing a total of approximately 36–38 recognised species. Duckweed is gaining attention in nutrition and food sciences due to its potential as a sustainable source of protein, vitamins, minerals, and other bioactive compounds. However, there are several gaps in research specifically focused on nutrition and the bioaccessibility of its components. While some studies have analysed the variability in the nutritional composition of different duckweed species, there is a need for comprehensive research on the variability in nutrient contents across species, growth conditions, harvesting times, and geographic locations. There has been limited research on the digestibility, bioaccessibility (the proportion of nutrients that are released from the food matrix during digestion), and bioavailability (the proportion that is absorbed and utilised by the body) of nutrients in duckweed. Furthermore, more studies are needed to understand how food processing (milling, fermentation, cooking, etc.), preparation methods, and digestive physiology affect the nutritional value and bioavailability of the essential bioactive components in duckweed and in food matrices supplemented with duckweed. This could help to optimise the use of duckweed in human diets (e.g., hamburgers or pastas supplemented with duckweed) or animal feed. More research is needed on how to effectively incorporate duckweed into diverse cuisines and dietary patterns. Studies focusing on recipe development, consumer acceptance, palatability, and odour are critical. Addressing these gaps could provide valuable insights into the nutritional potential of duckweed and support its promotion as a sustainable food source, thereby contributing to food security and improved nutrition. In summary, this article covers the general knowledge of duckweed, its important nutritional values, factors that may affect their biological value, and risk factors for the human diet, while looking for technological solutions (covering traditional and novel technologies) that can be used to increase the release of the useful, health-promoting components of duckweed and, thus, their bioavailability. This article, identifying gaps in recent research, could serve as a helpful basis for related research in the future. Duckweed species with good properties could be selected by these research studies and then included in the human diet after they have been tested for food safety.

Serratia marcescens strains from a dairy-producing environment were tested for their inhibitory effect on Listeria monocytogenes, Salmonella Hartford, Yersinia enterocolitica and Escherichia coli. Inhibition of foodborne pathogens was observed in the case of a non-pigmented Serratia strain, while the pigment-producing isolate was able to inhibit only Y. enterocolitica. The co-culturing study in tryptone soya broth (TSB) and milk showed that the growth of Salmonella was inhibited in the first 24 h, but later the pathogen could grow in the presence of the Serratia strain even if its cell concentration was 1000 times higher than that of Salmonella. However, we found that (1) concentrated cell-free supernatants had stronger inhibitory activity, which confirms the extracellular nature of the antagonistic compound(s). We proved that (2) protease and chitinase enzymes can take part in this mechanism, but they are not the main inhibitory compounds. The presence of prodigiosin was observed only in the case of the pigmented strain; thus, (3) we hypothesized that prodigiosin does not take part in the inhibition of the pathogens. However, (4) the combined effect of different extracellular metabolites might be attributed to the inhibitory property. Application of concentrated S. marcescens cell-free supernatant can be an effective antibacterial strategy in the food industry, mainly in the form of a bio-disinfectant on surfaces of food-processing areas.