Nanostructured chitosan/propolis formulations: characterization and effect on the growth of Aspergillus flavus and production of aflatoxins

Abstract

A great diversity of agricultural products is susceptible to contamination caused by Aspergillus flavus . To reduce fungal contamination, the application of natural products has been proposed, including chitosan and propolis, due to its broad and recognized antimicrobial activity on several microorganisms. Currently, the application of nanotechnology allows for a greater activity to be more reactive and efficient. The objectives of this research were to characterize by TEM and Z potential some of the studied nanoparticles and to determine the in vitro antifungal activity of the formulations and the production of aflatoxins of the treated fungus. For this, individual treatments and different nanoformulations were elaborated by varying the percentage of the components such as chitosan solution, chitosan nanoparticles, an extract of propolis, nanoparticles of propolis, glycerol and canola oil. The final concentrations of the formulations were of 20%, 30% and 40% and the control consisted of Czapeck-dox agar medium. TEM micrographies showed a spherical morphology in a range of 2.3–3.0 nm with values of Z potential from 18.5 to 116.2 nm. Compared to the untreated fungus, the highest effect was seen in the parameter of spore germination, since inhibition was of c. a. 97% corresponding to the formulation containing chitosan + propolis nanoparticles + chitosan nanoparticles + propolis extract at the highest concentration of 40%. At this same concentration, the production of aflatoxins was 100% inhibited with the treatment with chitosan at 1%. Since these results are under carefully controlled conditions, further research should be extended to different fruit and vegetables affected by this fungus.

Edible Chitosan/Propolis Coatings and Their Effect on Ripening, Development of Aspergillus flavus, and Sensory Quality in Fig Fruit, during Controlled Storage

“…Moreover, in previous studies carried out by Cortes-Higareda et al [ 7 ] the nanostructured coatings based on chitosan at 0.05% and propolis at 40% notably inhibited the mycelial growth of A. flavus by up to 30% and, most importantly, the production of aflatoxins by <2.8 ppb. However, before further recommendation, it was necessary to evaluate the effect of these coatings on the storage life of fresh figs.…”

“…Medium molecular weight chitosan concentrations of 1.0% was prepared by adding an equal amount ( w / v 1:1) of acetic acid to chitosan. The chitosan-acetic acid mixture was added to the total volume of distilled water [ 7 ]. This was stirred for 24 h at room temperature.…”

“…The chitosan and propolis nanoparticles were synthetized according to the methodology proposed by Cortes-Higareda et al [ 7 ]. Low molecular chitosan solutions at concentrations of 0.05% ( w / v ) were dissolved in glacial acetic acid (1% v / v ) and distilled water.…”

“…Subsequently, the column was rinsed with double distilled water; 1 mL of high-performance liquid chromatography (HPLC) grade methanol was passed through the column and recovered for introduction to a multiple wavelength fluorescence detector (VICAM, Series-4) using 365 nm excitation and 440 nm emission for aflatoxin detection. The data were expressed in parts per billion (ppb) of total aflatoxins [ 7 ].…”

“…Previous researchers have shown that edible coatings based on natural, biodegradable, and non-toxic compounds such as chitosan (CS) and propolis (P) can provide antimicrobial activity against a wide variety of phytopathogenic fungi, including the genus Aspergillus [ 6 , 7 ]. To potentiate the reactivity of these compounds, it has been proposed to take advantage of nanotechnology [ 8 ].…”