Potencial antifúngico de constituintes de óleos essenciais

Os produtos naturais são importantes fontes para o desenvolvimento de novos agentes medicinais e, devido ao potencial biológico e farmacológico desses compostos, torna-se necessário realizar estudos que viabilizem sua aplicação. Objetivou-se neste trabalho avaliar o potencial antifúngico de determinados constituintes de óleos essenciais. A avaliação do efeito inibitório dos compostos p-cimeno, eugenol, carvacrol, citral, trans-cariofileno e trans-farnesol foi testada sobre os fungos Aspergillus carbonarius, Aspergillus flavus, Aspergillus ochraceus e Aspergillus niger, empregando-se a metodologia de difusão em disco. Avaliou-se o efeito dos compostos eugenol, carvacrol e citral sobre o crescimento micelial dos fungos A. carbonarius e A. niger em diferentes temperaturas. A análise da atividade inibitória dos fungos revelou que os compostos eugenol, carvacrol e citral mostraram maior capacidade em inibir o crescimento dos micro-organismos avaliados. Esses constituintes também influenciaram o crescimento micelial dos fungos A. niger e A. carbonarius em diferentes temperaturas, sendo as temperaturas de 20 ºC e 25 ºC mais propícias para o desenvolvimento dos fungos. Os resultados encontrados mostraram-se promissores na busca por compostos bioativos. Estudos envolvendo esses constituintes podem ser relevantes em outras atividades, bem como em associação com os compostos sintéticos já empregados a fim de diminuir a toxicidade e resistência dos mesmos e avaliar o efeito sinérgico entre eles.

SORPTION OF HEAVY METALS BY MOLD FUNGUS ASPERGILLUS CARBONARIUS MELANIZING CARDBOARD

It has been shown that the mould fungus Aspergillus carbonarius, which synthesizes extracellular melanin, is able to develop due to the degradation of cellulose inside the cardboard under conditions of low water availability. The maximum yield of melanin was noted in a slightly alkaline medium, but in the presence of copper ions, a high level of pigmentation of the medium is also observed at low pH values. Melanized mycelium and exomelanin are characterized by a high sorption capacity in relation to heavy metal ions present in printing pigments of waste paper. In the process of growth A. carbonarius decreases acidity from neutral values to pH 2.8–3.1, increases the mobility of heavy metals immobilized on cellulose fibers and binds them by functional groups via ionic or chelating pathways. The sorption capacity of biomass with respect to copper, zinc, and nickel ions increased in the order of viable mycelium < inactivated mycelium < exomelanin. Lead ions were most actively bound by inactivated mycelium. The extracellular pigment accumulated copper better than other metals. The distribution coefficient in the system melanin – Cu2+ reached 1390 ml/g.

Towards Biological Control of Aspergillus carbonarius and Botrytis cinerea in Grapevine Berries and Transcriptomic Changes of Genes Encoding Pathogenesis-Related (PR) Proteins

Grapevine bunch rot, caused by Botrytis cinerea and Aspergillus carbonarius, causes important economic losses every year in grape production. In the present study, we examined the plant protective activity of the biological control agents, Paenibacillus alvei K165, Blastobotrys sp. FP12 and Arthrobacter sp. FP15 against B. cinerea and A. carbonarius on grapes. The in vitro experiments showed that strain K165 significantly reduced the growth of both fungi, while FP15 restricted the growth of A. carbonarius and FP12 was ineffective. Following the in vitro experiments, we conducted in planta experiments on grape berries. It was shown that K165, FP12 and FP15 reduced A. carbonarius rot severity by 81%, 57% and 37%, respectively, compared to the control, whereas, in the case of B. cinerea, the only protective treatment was that with K165, which reduced rot by 75%. The transcriptomic analysis of the genes encoding the pathogenesis-related proteins PR2, PR3, PR4 and PR5 indicates the activation of multiple defense responses involved in the biocontrol activity of the examined biocontrol agents.

Effects of Light on the Ochratoxigenic Fungi Aspergillus ochraceus and A. carbonarius

Ochratoxin A (OTA) usually contaminates agricultural products such as grapes, oatmeal, coffee and spices. Light was reported as an effective strategy to control spoilage fungi and mycotoxins. This research investigated the effects of light with different wavelengths on the growth and the production of OTA in Aspergillus ochraceus and Aspergillus carbonarius. The results showed that the growth of both fungi were extremely inhibited by UV-B. Short-wavelength (blue, violet) significantly inhibited the production of OTA in both fungi, while the inhibitory effect of white was only demonstrated on A. ochraceus. These results were supported by the expression profiles of OTA biosynthetic genes of A. ochraceus and A. carbonarius. To clarify, the decrease in OTA production is induced by inhibition or degradation; therefore, the degradation of OTA under different wavelengths of light was tested. Under UV-B, the degradation rate of 10 μg/mL OTA standard pure-solution samples could reach 96.50% in 15 days, and the degradation effect of blue light was relatively weak. Furthermore, infection experiments of pears showed that the pathogenicity of both fungi was significantly decreased under UV-B radiation. Thus, these results suggested that light could be used as a potential target for strategies in the prevention and control of ochratoxigenic fungi.