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ABSTRACT: Rhizosphere microorganisms play an important role in the growth and health of plants. Around the world, diverse soil-borne pathogens attack Capsicum annuum causing significant damage and economic losses. This study determined whether the diversity and composition of microbial communities in the rhizosphere soil of C. annuum plants is significantly changed by wilt disease. We used the 16S rRNA gene for bacteria and the internal transcribed spacer region for fungi to characterize the rhizosphere microbiomes of healthy and wilted plants. The most abundant bacterial phyla were Proteobacteria and Gemmatimonadetes, while the most abundant fungal phyla were Ascomycota and Mucoromycota. The bacterial α-diversity did not show significant differences in richness and diversity, but did show a significant difference in evenness and dominance of species. Rare taxa were present in both healthy and wilted conditions with relative abundances < 1%. In the fungi, all evaluated estimators showed a significant reduction in the wilted condition. The β-diversity showed significant differences in the structure of bacterial and fungal communities, which were segregated according to plant health conditions. The same occurred when comparing the alpha and beta diversity of this study based on organic agriculture with that of other studies based on conventional agriculture. We observed a significant difference with estimators analyzed by segregating rhizosphere communities depending on the farming method used. Finally, the differential abundance analysis did not show significant results in the bacterial communities; however, in the fungal communities, Fusarium, Thanatephorus, Rhizopus, Curvularia, Cladosporium, and Alternaria were more abundant in the rhizosphere of wilted than healthy plants. Species from these genera have been previously reported as phytopathogens of several plants, including C. annuum.

RESUMO: Microrganismos na rizosfera desempenham um papel importante no crescimento e saúde das plantas. Em todo o mundo, vários patógenos do solo atacam o Capsicum annuum causando danos significativos e perdas econômicas. Este estudo teve como objetivo determinar se a diversidade e composição das comunidades microbianas no solo da rizosfera de plantas de C. annuum é alterada significativamente pela murcha. Usamos o gene 16S rRNA para bactérias e a região espaçadora transcrita interna para fungos para caracterizar os microbiomas da rizosfera de plantas saudáveis e plantas com murcha. Os filos bacterianos mais abundantes foram Proteobacteria e Gemmatimonadetes, enquanto os filos fúngicos foram Ascomycota e Mucoromycota. A diversidade alfa bacteriana não mostrou diferenças significativas na riqueza e diversidade, mas mostrou uma diferença significativa na uniformidade e dominância das espécies. Táxons raros estavam presentes em condições saudáveis e murchas com abundância relativa < 1%. Em fungos, todos os estimadores avaliados apresentaram redução significativa na condição de murcha. A diversidade beta apresentou diferenças significativas na estrutura das comunidades bacterianas e fúngicas, que foram segregadas de acordo com as condições fitossanitárias. O mesmo aconteceu ao comparar a diversidade alfa e beta deste estudo baseado na agricultura orgânica com a de outros estudos baseados na agricultura convencional. Uma diferença significativa foi observada com os estimadores analisados segregando as comunidades da rizosfera dependendo do método de cultivo utilizado. Por fim, a análise de abundância diferencial não apresentou resultados significativos nas comunidades bacterianas; entretanto, nas comunidades fúngicas, os gêneros Fusarium, Thanatephorus, Rhizopus, Curvularia, Cladosporium e Alternaria foram mais abundantes na rizosfera de plantas murchas do que saudáveis. Várias espécies desses gêneros foram previamente relatadas como fitopatógenos de várias plantas, incluindo C. annuum.

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Polyphenols, as secondary metabolites from plants, possess a natural antioxidant capacity and biological activities attributed to their chemical and structural characteristics. Due to their mostly polar character, polyphenols present a low solubility in less polar environments or hydrophobic matrices. However, in order to make polyphenols able to incorporate in oils and fats, a transformation strategy is necessary. For the above, the functionalization of polyphenols through chemical or enzymatic lipophilization has allowed the synthesis of phenolipids. These are amphipilic molecules that preserve the natural phenolic core to which an aliphatic motif is attached by esterification or transesterification reactions. The length of the aliphatic chain in phenolipids allows them to interact with different systems (such as emulsions, oily molecules, micelles and cellular membranes), which would favor their use in processed foods, as vehicles for drugs, antimicrobial agents, antioxidants in the cosmetic industry and even in the treatment of degenerative diseases related to oxidative stress.

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Compounds from spices and herbs extracts are being explored as natural antibacterial additives. A plant extract used in traditional folk medicine is Hibiscus sabdariffa L., also known as Roselle. Therefore, the potential use of a phenolic hibiscus extract as antibacterial or natural food preservative was analyzed in vitro and in situ. A phenolic extract was obtained from hibiscus calyces and fractionated, and then the fractions were tested against foodborne pathogen bacteria. Liquid-liquid extraction and solid-phase extraction were used to fractionate the hibiscus extract, and HPLC was employed to analyze the fractions' phenolic composition. Minimum bactericidal concentration (MBC) and minimal inhibitory concentration (MIC) were calculated for brute hibiscus phenolic extract, each of the fractions and pure commercial phenolic compounds. Bacteria tested were Escherichia coli, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Listeria monocytogenes and Bacillus cereus. The fraction obtained after liquid-liquid extraction presented the best performance of MBC and MIC against the bacteria tested. Furthermore, a hibiscus ethanolic extract was employed as a natural preservative to extend the shelf-life of beef. Microbiological, color and sensory analyses were performed to the meat during the shelf-life test. The application of the phenolic hibiscus extract also showed an increase of the duration of the meat`s shelf life.

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Antifungal and sensorial properties of spices have been recognized for years. The antifungal compounds are products of the plant's secondary metabolism, and the action of those compounds could be used to inhibit the growth of spoilage and pathogenic microorganisms in food. Mexican oregano (Lippia berlandieri) grows wildly in the desert zone of Mexico and is usually added to regional foods. The goal of this study was to evaluate the antifungal activity of Mexican oregano versus food-contaminant fungi. Fungi were isolated from spoiled fruit and vegetables and identified according to morphological characteristics. The antifungal activity of oregano was evaluated by radial growth measurement on potato dextrose agar added with dried oregano (0.25 to 4.0%). The essential oil antifungal activity of oregano was also evaluated by the diffusion well test. Twenty-one fungal strains were isolated, which included Penicillium, Geotrichum, Aspergillus, and Bipolaris. In seven of the 21 strains, no inhibitory effect was observed at either concentration of oregano. An increase in growth at the lower or higher concentrations of oregano, when compared to the control, was observed in two fungal strains; in 12 strains, a strong inhibitory effect of oregano was evident. The oregano essential oil was inhibitory to all fungal strains, but there were differences in the extent of the effect. Although the antifungal effect of oregano is strongly established, there was a differential effect with the fungal strains studied. Besides pathogenic fungi and bacteria, microbial spoilage flora should be considered when the addition of spices for food preservation is proposed.

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