Cymbopogon citratus Essential Oil: Its Application as an Antimicrobial Agent in Food Preservation

Antimicrobial in vitro and in situ efficacies of Cymbopogon citratus essential oil (lemongrass, LGEO) against 17 spoilage microorganisms (bacteria, yeasts and fungi) were evaluated. Additionally, its chemical composition, and antioxidant and antibiofilm activities were investigated. The LGEO exhibited a strong antioxidant activity (84.0 ± 0.1%), and its main constituents were citral (61.5%), geraniol (6.6%) and 1,8-cineole (6.4%). An in vitro antimicrobial evaluation revealed the lowest inhibition zone (1.00 ± 0.00 mm) in Pseudomonas fluorescens, and the highest inhibition zone (18.00 ± 2.46 mm) in Candida krusei. The values for the minimal inhibitory concentration were determined to be the lowest for Salmonella enteritidis and the highest for C. albicans. Furthermore, the concentration of ≥250 µL/L of LGEO suppressed the growth of Penicillium aurantiogriseum, Penicillium expansum, Penicillium chrysogenum and Penicillium italicum. The changes in the molecular structure of the biofilms produced by Pseudomonas fluorescens and Salmonella enteritidis, after their treatment with LGEO, confirmed its action on both biofilm-forming bacteria. Moreover, an in situ antimicrobial activity evaluation displayed the most effective inhibitory effectiveness of LGEO against Micrococcus luteus, Serratia marcescens (250 µL/L) and Penicillium expansum (125, 250 and 500 µL/L) growing on a carrot. Our results suggest that LGEO, as a promising natural antimicrobial agent, can be applied in the innovative packaging of bakery products and different types of vegetables, which combines commonly used packing materials with the addition of LGEO.

Study on the effect of fengycin on the respiration and metabolic mechanism of Penicillium expansum

This study investigate the inhibiting effect of fengycin on respiration and nutrient utilization of Penicillium expansum. The respiratory inhibition rate of the P. expansum was determined by the test of dissolved oxygen fengycin, The effect of fengycin treatment on the activity of P. expansum mitochondrial complex enzyme was detected by mitochondrial enzyme activity assay. The ability of fengycin treatment to P. expansum the utilization of total sugar and total protein was determined by DNS colorimetric method and biuret method. After fengycin treatments, the TCA pathway of respiratory metabolism in P. expansum was inhibited. Besides, fengycin could block the gene expression in P. expansum by binding P. expansum mitochondrial complex enzyme II and III related genes. Therefore, the activity of mitochondrial enzymes was affected. With the increasement of fengycin concentration, the absorption and utilization capacity of P. expansum to total sugar and total protein decreased significantly. Fengycin could inhibit the respiratory metabolism and reduce the biochemical metabolism level in P. expansum and finally caused the growth inhibition.

Chemical strategies for triggering the immune response to the mycotoxin patulin

Mycotoxins represent a major concern for human and animal health because of their harmful effects and high occurrence in food and feed. Rapid immunoanalytical methods greatly contribute to strengthening the safety of our food supply by efficiently monitoring chemical contaminants, so high-affinity and specific antibodies have been generated for almost all internationally regulated mycotoxins. The only exception is patulin, a mycotoxin mainly produced by Penicillium expansum for which such a target has not yet been achieved. Accordingly, no point-of-need tests commonly used in food immunodiagnostics are commercially available for patulin. In the present study, three functionalized derivatives conforming to generally accepted rules in hapten design were firstly tested to generate suitable antibodies for the sensitive immunodetection of patulin. However, these conventional bioconjugates were unable to elicit the desired immune response, so an alternative strategy that takes advantage of the high electrophilic reactivity of patulin was explored. Patulin was reacted with 4-bromothiophenol, and the obtained adduct was used to produce antibodies with nanomolar affinity values. These results demonstrated for the first time that targeting the adduct resulting from the reaction of patulin with a thiol-containing compound is a promising approach for developing user-friendly immunoanalytical techniques for this elusive mycotoxin.

Patulin-producing mold, toxicological, biosynthesis, and molecular detection of patulin

Mycotoxin is one of the food safety problems that raise concern because of its negative health impact and significant economic losses. Patulin is the most common mycotoxin found in fruits and its products like apple, orange, grape, pear, etc. There are 167 species reported to produce patulin; Penicillium expansum is the major patulin producer among those fungi species. Patulin is not classifiable as to its carcinogenicity to humans, but some studies showed the toxicities of patulin. Patulin has a broad spectrum of toxicity such as acute toxicity, sub-acute toxicity, genotoxicity, embryotoxicity and teratogenicity, carcinogenicity, and immunotoxicity. There are several ways to detect mycotoxins, such as HPLC, TLC, ELISA, and PCR. The popular way to detect mycotoxin molecularly is PCR because of its sensitivity and specificity. To detect patulin molecularly require proper selection of target gene. Therefore, the biosynthesis of patulin, its influencing gene, and its underlying factor needs to be understood.