Nanofibrous matrices containing hop leaves extracts for the control of american foulbrood

GIMÉNEZ MARTÍNEZ, PABLO D.; KLOSTER, GIANINA A.; MÉNDEZ, CARLOS; PEGORARO, CÉSAR; MEDICI SANDRA; RIVERO, GUADALUPE; FUSELLI, SANDRA R.

Belgrado

Congreso; EurBee 9 - 9th European Congress of Apidology; 2022

University of Belgrade - Faculty of Biology

In recent years, natural compounds have been investigated for controlling beekeeping pathologies due to the presence of residues and the generation of resistance by synthetic compounds. Abundant sources of bioactive compounds are agro-industrial waste, which through the implementation of a circular bio-economy are given added value. An example of waste is the hops leaves (Humulus lupulus), whose flower is the important product for the brewing industry, so after its collection, the leaves generate a large amount of organic matter that is harmful to the environment.Previous studies by our research group found that hydroalcoholic extracts from hop leaves have good antimicrobial activity against Paenibacillus larvae and they are not toxic to bees.Electrospinning techniques are currently used for the preparation of nanofibers capable of immobilizing different types of active agents, which can be gradually released. In short, a high electric potential is applied to polymer-based solutions infused through a nozzle with a controlled rate, so that submicrometric fibers can be collected. The objective of this work is: 1) to prepare polymeric nanofibers containing hydroalcoholic extracts of hop leaves via electrospinning process, 2) to characterize the morphology, physicochemical and thermal properties by various techniques, 3) to analyze the antimicrobial activity against P. larvae and 4) to evaluate their toxicity to bees when consumed. Eudragit L100-55 was chosen as polymer matrix, given its selective dissolution at pH>5.5. The formation of uniform submicrometric fibers was corroborated by scanning electron microscopy (SEM) while the presence of carbonyl groups corresponding to the extracts was observed in the nanofibrous membranes by means of Fourier Transform Infrared Spectroscopy (FTIR-ATR). Regarding the antimicrobial activity against P. larvae, the growth of the strains was inhibited once the membrane was dissolved. Finally, both the loaded and control matrices showed no toxicity to bees when consumed.These results are a potential new application of natural compounds in the hive that could provide antimicrobial activity without generating toxic residues in the commercial products.