Desenvolvimento de nanofibras incorporadas com óleos essenciais de cravo, tomilho e capim-limão para o controle in vitro de Penicillium digitatum

Abstract

Penicillium digitatum is an important citrus postharvest pathogen that causes major economic losses. The control of this pathogen is carried out with synthetic fungicides and, due to the concern with the toxicity caused by the fungicides, the search for alternative methods of control, such as the use of essential oils, is growing. Essential oils are well known for their antimicrobial activities, however they present high volatility and easy degradation by light, heat and oxygen and may limit its action. Given this, nanoencapsulation can contribute to its preservation in addition to allowing a controlled release of active compounds. Therefore, this work aimed to produce nanofibers incorporated with essential oils and to verify their effect in vitro against Penicillium digitatum. Poly (lactic acid) (PLA) nanofibers containing essential oils (OE) of clove, thyme and lemongrass were produced using the solution blowing (SBS) spinning technique in a centroid-simplex mixture experimental design, with three replicates from the central point, and applied in vitro against Penicillium digitatum. Optical microscopy was used to identify Penicillium digitatum, and Gas Chromatography - Mass Spectrometry (GC-MS) to characterize essential oils. PLA-OE fibers were characterized using a scanning electron microscope (SEM) and infrared spectrometry with Fourier transform (FTIR). The main compounds of essential oils of clove, thyme and lemongrass were eugenol (83.79%); p-cymene (46.98%) and thymol (18.23%) and; geranial (42.69%) and neral (33.53%), respectively. FTIR analyzes of all nanofibers containing essential oil revealed the presence of characteristic peaks of each oil. The micrographs made it possible to observe fibers in a random arrangement and with different diameters and the presence of spheres in all treatments. Through the centroide-simplex design, it was observed that the nanofibers applied by the fumigation method showed better results and, among them, the nanofiber containing essential clove oil was the most effective with 71.79% inhibition of mycelial growth of Penicillium digitatum. The response surface and the special cubic statistical model equation indicated the formulation with 100% OE of cloves as the optimal formulation for the in vitro control of Penicillium digitatum. These results confirm the potential of SBS nanofibers incorporated with essential oil for the in vitro control of Penicillium digitatum.