Microbial antagonists to biologically control postharvest decay and preserve fruit quality

Organic nanoparticles incorporated starch/carboxymethylcellulose multifunctional coating film for efficient preservation of perishable products

Most of postharvest agricultural produces are perishable due to microorganisms infections and physiological change. Herein, one kind of multifunctional coating film of SC-ECCNPs was developed by incorporating organic nanoparticles of ECCNPs into starch/carboxymethylcellulose (SC) to prolong shelf life of food with excellent performances. The SC-ECCNPs coating was prepared with starch and sodium carboxymethylcellulose as film substrate (SC) to incorporate with organic nanoparticles of ECCNPs formed by integrating epigallocatechin-3-gallate (EGCG), cysteine (Cys), and cinnamaldehyde (CA). The incorporation of ECCNPs improves the UV-resistance and physical properties of SC-ECCNPs coating and also endows it with excellent antioxidative and broad-spectrum antibacterial activity. The application possibilities of SC-ECCNPs coating were explored with strawberries and oranges as samples, validating that the SC-ECCNPs coating can prolong the shelf life of fruits at room temperature. The biosafety of the coating was further confirmed with hemolysis and MTT experiments. The SC-ECCNPs coating film was prepared with natural substrates via a simple and green method. The investigation provides an instructive way for developing advanced packaging materials with high performances.

2-Heptanol inhibits Botrytis cinerea by accelerating amino acid metabolism and retarding membrane transport

During the postharvest storage of tomatoes, they are susceptible to infection by Botrytis cinerea, leading to significant economic losses. This study evaluated the antifungal potential of 2-heptanol (2-HE), a volatile biogenic compound, against B. cinerea and explored the underlying antifungal mechanism. The results indicated that 2-HE effectively suppressed the growth of B. cinerea mycelia both in vivo and in vitro and stimulated the activities of antioxidative enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in tomatoes. Furthermore, 2-HE reduced spore viability, compromised membrane integrity, and resulted in increased levels of extracellular nucleic acids, protein content, and membrane lipid peroxidation. Transcriptomic analysis revealed that 2-HE disrupted the membrane transport system and enhanced amino acid metabolism, which led to intracellular nutrient depletion and subsequent B. cinerea cell death. Additionally, the 2-HE treatment did not negatively impact the appearance or quality of the tomatoes. In conclusion, the findings of this study offer insights into the use of 2-HE as a biocontrol agent in food and agricultural applications.

Bioprotective yeasts: Potential to limit postharvest spoilage and to extend shelf life or improve microbial safety of processed foods

Yeasts are a widespread group of microorganisms that are receiving increasing attention from scientists and industry. Their diverse biological activities and broad-spectrum antifungal activity make them promising candidates for application, especially in postharvest biocontrol of fruits and vegetables and food biopreservation. The present review focuses on recent knowledge of the mechanisms by which yeasts inhibit pathogenic fungi and/or spoilage fungi and bacteria. The main mechanisms of action of bioprotective yeasts include competition for nutrients and space, synthesis and secretion of antibacterial compounds, mycoparasitism and the secretion of lytic enzymes, biofilm formation, quorum sensing, induced systemic resistance of fruit host, as well as the production of reactive oxygen species. Preadaptation of yeasts to abiotic stresses such as cold acclimatization and sublethal oxidative stress can improve the effectiveness of antagonistic yeasts and thus more effectively play biocontrol roles under a wider range of environmental conditions, thereby reducing economic losses. Combined application with other antimicrobial substances can effectively improve the efficacy of yeasts as biocontrol agents. Yeasts show great potential as substitute for chemical additives in various food fields, but their commercialization is still limited. Hence, additional investigation is required to explore the prospective advancements of yeasts in the field of biopreservation for food.

Glycine Enhances Oxidative Stress Tolerance and Biocontrol Efficacy of Sporidiobolus pararoseus against Aspergillus niger Decay of Apples

Apples are deeply loved by people because of their rich nutritional value, but they are susceptible to rotting. The use of antagonistic yeast is a promising method for controlling postharvest fruit diseases, but biocontrol efficacy of yeast will be weakened in environmental stress. In this study, the effects of glycine (Gly) on the oxidative stress tolerance and the biocontrol efficacy of Sporidiobolus pararoseus (S. pararoseus) against Aspergillus niger (A. niger) are discussed. Under the stimulation of H2O2, the yeast cells treated with Gly (1 mM) showed lower ROS content, less mitochondrial impairment and cellular oxidative damage, and the cell survival rate was significantly higher than Gly-untreated yeast. The yeast cells exposed to Gly significantly increased the activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and the content of glutathione (GSH). Notably, Gly-treated yeast cells had better biocontrol efficacy against A. niger in postharvest apples. The lesion diameter and decay incidence were reduced by 17.67 mm and 79.63% compared to the control, respectively, when S. pararoseus was treated with 1 mM Gly. Moreover, Gly-treated yeast increased the antioxidant enzymes activities and their gene expression were up-regulated in apples. These results indicated that 1 mM Gly not only reduced the oxidative damage of yeast, but also induced resistance-related enzymes of apples under oxidative stress, which contributed to enhancing the biocontrol efficacy of S. pararoseus against A. niger in apples.