Biofilm containing the Thymus serpyllum essential oil for rice and cherry tomato conservation.

Introduction: Fungal pathogens cause major yield losses in agriculture and reduce food quality and production worldwide. Purpose: To evaluate new safer alternatives to chemicals for disease management and preserve the shelf life of food, this research was conducted to: determine the chemical composition of the essential oils (EOs) of Thymus serpyllum and Thymus piperella chemotypes 1 and 2; investigate the antifungal potential of EOs in vitro against: Alternaria alternata, Bipolaris spicifera, Curvularia hawaiiensis, Fusarium oxysporum f. sp. lycopersici, Penicillium italicum, Botryotinia fuckeliana; evaluate a natural T. serpyllum extract biofilm to conserve rice grain and cherry tomatoes. Method: EOs were analyzed by GC-MS+GC-FID. EOs' antifungal activity was evaluated by dissolving Thymus extracts in PDA. Petri dishes were inoculated with disks of each fungus and incubated at 25°C for 7 days. Results: The T. serpyllum EO displayed the best Mycelial Growth Inhibition. The antifungal effect of the T. serpyllum EO biofilm was evaluated on rice caryopsis. Disinfected grains were dipped in a conidial suspension of each fungus and sprayed with EO (300 and 600 µg/mL) prepared in Tween 20. Grains were stored. The percentage of infected grains was recorded for 30 days. The T. serpyllum EO effect on cherry tomato conservation was evaluated in vivo. Wounded fruit were immersed in the T. serpyllum EO (300 and 400 µg/mL) and inoculated with Fusarium oxysporum f. sp. lycopersici. Fruit were evaluated for 7 and 14 days. Chemical profiles thymol/carvacrol for T. serpyllum, carvacrol for T. piperella Tp1 and thymol for T. piperella Tp2 were defined. The three evaluated EOs reduced all the studied phytopathogens' fungal growth. The T. serpyllum biofilm was effective with rice storage and against Fusarium oxysporum f. sp. lycopersici for extending the shelf life of tomatoes in warehouses and storing postharvest cherry tomatoes. Conclusion: We suggest applying these EOs as biofilms for safe food conservation to replace synthetic products.

Evaluating the Antifungal Potential of Botanical Compounds to Control Botryotinia fuckeliana and Rhizoctonia solani.

The European Union is promoting regulatory changes to ban fungicides because of the impact their use has on the ecosystem and the adverse effects they can pose for humans. An ecofriendly alternative to these chemicals to fight against fungal species with low toxicity is essential oils and their compounds extracted from aromatic plants. The purpose of this study was to evaluate the in vitro antifungal capacity of the botanical compounds eugenol, carvacrol, thymol, and cinnamaldehyde, and the synergy or antagonism of their mixtures, against Botryotinia fuckeliana and Rhizoctonia solani. Different bioassays were performed at doses of 300, 200, 150, and 100 µg/mL using pure commercial compounds and their combination in potato dextrose agar culture medium. Growth rate and the mycelium growth inhibition parameters were calculated. Phenolic compounds and their combination inhibited the development of species at the different concentrations, with fungicidal or fungistatic activity shown under almost all the tested conditions. When comparing the growth rates of the species in the control plates and treatments, the statistical analysis showed that there were statistically significant differences. The mixture of compounds improved fungicidal activity against the studied species and at a lower concentration of monoterpenes.

Cherry tomato and persimmon kaki conservation with a natural and biodegradable film.

The chemical composition of Essential Oils Satureja montana and Mentha longifolia was determined, and their activity against important phytopathogenic and post-harvest fungi was studied, to evaluate their potential as natural food preservatives. The major compounds were carvacrol (24.0%), γ-terpinene (15.9%) and p-cymene (14.2%) in S. montana, and piperitenone oxide (52.7%) and piperitone oxide (23.5%) in M. longifolia. EOs were tested in vitro on Alternaria alternata, Botryotinia fuckeliana, Curvularia hawaiiensis, Fusarium equiseti, F. oxysporum lycopersici, Rhizoctonia solani and Verticillium dahliae. S. montana demonstrated excellent results. At 300 µg mL-1 the growth of all fungi was inhibited with 100% mycelial growth inhibition (MGI), except for B. fuckeliana (92%). M. longifolia was less effective, and its best result was against Verticillium dahliae (100% MGI) at 400 and 300 µg mL-1. S. montana EO was selected for in vivo antifungal tests in Cherry tomatoes and kaki "Persimmon" against A. alternata. The S. montana EO biofilm reduced post-harvest fungi development. In tomato, it inhibited up to 90% after 20 days. Necrosis did not occur for 2 months in the persimmon fruits. S. montana EO is an effective non-toxic preservative that can be considered to develop a botanical and enviro-friendly low-risk biofungicide.

Bomba Rice Conservation with a Natural Biofilm.

The chemical composition of commercial Syzygium aromaticum, Cinnamomum verum, and Laurus nobilis essential oils as well as their antifungal activity against four pathogenic fungi isolated from Mediterranean rice grains has been investigated. Eighty nine compounds accounting for between 98.5 and 99.4% of the total essential oil were identified. The phenylpropanoids eugenol (89.37 ± 0.29%) and eugenol (56.34 ± 0.41%), followed by eugenol acetate (19.48 ± 0.13%) were, respectively, the main compounds in clove and cinnamon essential oils, whereas large amounts of the oxygenated monoterpenes 1,8-cineole (58.07 ± 0.83%) and α-terpinyl acetate (13.05 ± 0.44%) were found in bay leaf essential oil. Clove and cinnamon oils showed the best antifungal activity results against all tested fungi. Against Alternaria alternata, clove essential oil displayed the best antifungal effect, whereas against Curvularia hawaiiensis, cinnamon essential oil was more active. Both essential oils showed a similar antifungal effect towards Fusarium proliferatum and Fusarium oxysporum. In vitro studies in inoculated rice grains showed that clove and cinnamon totally inhibited pathogenic fungal development after 30 days of incubation. In vivo studies showed that eugenol used with a polysaccharide such as agar-agar formed a fine coat which wraps the inoculated rice grains, creating a natural biofilm and reducing the development of all pathogenic fungi (80-95%) for 30 days.

Microscopy Characterization of Silica-Rich Agrowastes to be used in Cement Binders: Bamboo and Sugarcane Leaves.

Agrowastes are produced worldwide in huge quantities and they contain interesting elements for producing inorganic cementing binders, especially silicon. Conversion of agrowastes into ash is an interesting way of yielding raw material used in the manufacture of low-CO2 binders. Silica-rich ashes are preferred for preparing inorganic binders. Sugarcane leaves (Saccharum officinarum, SL) and bamboo leaves (Bambusa vulgaris, BvL and Bambusa gigantea, BgL), and their corresponding ashes (SLA, BvLA, and BgLA), were chosen as case studies. These samples were analyzed by means of optical microscopy, Cryo-scanning electron microscopy (SEM), SEM, and field emission scanning electron microscopy. Spodograms were obtained for BvLA and BgLA, which have high proportions of silicon, but no spodogram was obtained for SLA because of the low silicon content. Different types of phytoliths (specific cells, reservoirs of silica in plants) in the studied leaves were observed. These phytoliths maintained their form after calcination at temperatures in the 350-850°C range. Owing to the chemical composition of these ashes, they are of interest for use in cements and concrete because of their possible pozzolanic reactivity. However, the presence of significant amounts of K and Cl in the prepared ashes implies a limitation of their applications.

Commercial Origanum compactum Benth. and Cinnamomum zeylanicum Blume essential oils against natural mycoflora in Valencia rice.

Chemical composition of commercial Origanum compactum and Cinnamomum zeylanicum essential oils and the antifungal activity against pathogenic fungi isolated from Mediterranean rice grains have been investigated. Sixty-one compounds accounting for more than 99.5% of the total essential oil were identified by using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Carvacrol (43.26%), thymol (21.64%) and their biogenetic precursors p-cymene (13.95%) and γ-terpinene (11.28%) were the main compounds in oregano essential oil, while the phenylpropanoids, eugenol (62.75%), eugenol acetate (16.36%) and (E)-cinnamyl acetate (6.65%) were found in cinnamon essential oil. Both essential oils at 300 µg/mL showed antifungal activity against all tested strains. O. compactum essential oil showed the best antifungal activity towards Fusarium species and Bipolaris oryzae with a total inhibition of the mycelial growth. In inoculated rice grains at lower doses (100 and 200 µg/mL) significantly reduced the fungal infection, so O. compactum essential oil could be used as ecofriendly preservative for field and stored Valencia rice.