Influence of octanoic acid addition to medium on some volatile compounds and PR-toxin biosynthesis by Penicillium roqueforti

Potential Action Mechanism and Inhibition Efficacy of Morinda citrifolia Essential Oil and Octanoic Acid against Stagonosporopsis cucurbitacearum Infestations

The use of plant-based products has been shown to efficiently inhibit fungi-mediated diseases in agricultural crops. Here, we extracted and evaluated the composition of noni, Morinda citrifolia L., essential oil and assessed its activities against Stagonosporopsis cucurbitacearum in Cucumis melo L. Using in silico molecular approaches, potential interactions between the essential oil major components and S. cucurbitacearum tyrosine-tRNA ligase were predicted. Finally, we also measured the potential interference of plant physiology (the stomatal conductance and net photosynthesis) mediated by the application of the M. citrifolia essential oil. Chromatographic analysis revealed that octanoic acid (75.8%), hexanoic acid (12.8%), and isobutyl pent-4-enyl carbonate (3.1%) were the major essential oil compounds. Octanoic acid and noni essential oil, when used as preventive measures, reduce fungal mycelial growth at a concentration of 5 mg/mL without causing significant damage to the treated leaves, which reinforces their efficacies as preventive tools against S. cucurbitacearum. Molecular docking analyses predicted very stable interactions between the major essential oil constituents and S. cucurbitacearum tyrosine-tRNA ligase, suggesting the interference of these plant-based molecules upon enzyme activation. Octanoic acid and M. citrifolia essential oil at concentrations of 20 mg/mL decreased the stomatal conductance and net photosynthesis rate of melon plants, resulting in robust phytotoxicity. Collectively, our findings indicated that despite the phytotoxicity risks at higher concentrations, M. citrifolia essential oil and octanoic acid, have potential as alternative tools for the integrative management of S. cucurbitacearum.

PR Toxin - Biosynthesis, Genetic Regulation, Toxicological Potential, Prevention and Control Measures: Overview and Challenges

Out of the various mycotoxigenic food and feed contaminant, the fungal species belonging to Penicillium genera, particularly Penicillium roqueforti is of great economic importance, and well known for its crucial role in the manufacturing of Roquefort and Gorgonzola cheese. The mycotoxicosis effect of this mold is due to secretion of several metabolites, of which PR toxin is of considerable importance, with regard to food quality and safety challenges issues. The food products and silages enriched with PR toxin could lead into damage to vital internal organs, gastrointestinal perturbations, carcinogenicity, immunotoxicity, necrosis, and enzyme inhibition. Moreover, it also has the significant mutagenic potential to disrupt/alter the crucial processes like DNA replication, transcription, and translation at the molecular level. The high genetic diversities in between the various strains of P. roqueforti persuaded their nominations with Protected Geographical Indication (PGI), accordingly to the cheese type, they have been employed. Recently, the biosynthetic mechanism and toxicogenetic studies unraveled the role of ari1 and prx gene clusters that cross-talk with the synthesis of other metabolites or involve other cross-regulatory pathways to negatively regulate/inhibit the other biosynthetic route targeted for production of a strain-specific metabolites. Interestingly, the chemical conversion that imparts toxic properties to PR toxin is the substitution/oxidation of functional hydroxyl group (-OH) to aldehyde group (-CHO). The rapid conversion of PR toxin to the other derivatives such as PR imine, PR amide, and PR acid, based on conditions available reflects their unstability and degradative aspects. Since the PR toxin-induced toxicity could not be eliminated safely, the assessment of dose-response and other pharmacological aspects for its safe consumption is indispensable. The present review describes the natural occurrences, diversity, biosynthesis, genetics, toxicological aspects, control and prevention strategies, and other management aspects of PR toxin with paying special attention on economic impacts with intended legislations for avoiding PR toxin contamination with respect to food security and other biosafety purposes.

Key Odorants of Lazur, a Polish Mold-Ripened Cheese

Application of gas chromatography-olfactometry (GC-O) carried out on the volatile fraction isolated by solvent-assisted flavor evaporation (SAFE) and solid phase microextraction (SPME) from Lazur mold-ripened cheese revealed 17 odor-active compounds. The highest flavor dilution factor (FD) has been obtained for methanethiol (2048) with a burnt odor note and for 2(3)-methylbutanoic acid (2048) with a cheesy, pungent odor. Further quantitation of the 15 most aroma-active compounds allowed for calculation of their odor activity values (OAV). The highest OAVs were obtained for methanethiol (500), 3(2)-methylbutanoic acid (321), 3-(methylthio)propanal (210), 2,3-butanedione (65), dimethyl trisulfide (22), butanoic acid (20), 1-octen-3-ol (18), ( Z)-4-heptenal (14), dimethyl disulfide (14), dimethyl sulfide (13), phenylacetaldehyde (6), 2-ethyl-3,5-dimethylpyrazine (5), and acetic acid (4). An aroma recombination experiment showed slight differences in the perception of cheesy/sweaty and moldy/musty notes. To verify the influence of methyl ketones on the aroma profile of mold-ripened cheese, recombinant has been additionally supplemented with 2-pentanone, 2-heptanone, and 2-nonanone in concentrations determined in Lazur cheese. The aroma profile remained unchanged, which would suggest that methyl ketones, in this particular cheese, do not play a significant role in the formation of aroma.

Characterization of some mushroom and earthy off-odors microbially induced by the development of rot on grapes

Grape rot is one of the major causes of degradation of many grape components and, thus, of deterioration in wine quality. In particular, the association of Botrytis cinerea with other, less visible, fungi frequently leads to the development of organoleptic defects in grapes and sometimes in wines. This study examines the nature of the volatile compounds responsible for mushroom, mossy, or earthy odors detected by gas chromatography-olfactometry in organic extracts of rotten grapes and musts. 2-Methylisoborneol, (-)-geosmin, 1-octen-3-one, 1-octen-3-ol, 2-octen-1-ol, and 2-heptanol were identified or tentatively identified. Their concentrations in musts were determined, and the impact of alcoholic fermentation by the yeast Saccharomyces cerevisiae was studied. The ability of fungi isolated from rotten grapes (Botrytis cinerea; Penicillium species including P. brevicompactum, P. expansum, P. miczynskii, P. pinophilum, P. purpurogenum, and P. thomii; Aspergillus section nigri; Rhizopus nigricans; and Coniothyrium sp.) to produce some of the identified compounds was evidenced.