EHDAnguilla – Application of electrohydrodynamic atomization as a tool to produce high protein content micrometric capsules to feed larval phase Anguilla.

Electrohydrodynamic atomization (EHDA) is a technique which uses strong electric fields (kV per centimeter)
to manipulate the breaking up of a liquid into droplets and produce droplets which are many times smaller than
the nozzle diameter, with a narrow size distribution. Also, when applied in a coaxial nozzle configuration, it
allows to produce encapsulated particles. In this project, coaxial EHDA was used to produce high protein
content micrometric capsules to feed eel larvae and solve one of the challenges of eel growth in aquaculture.
One of the major limitations of this process is the lack of a suitable diet to feed the larvae: the one that is
currently in use is, indeed, unhygienic and pollutant for the tanks where the eels are placed, thus not
sustainable environmentally and economically.
The main goal of the project was to replace this liquid diet with micrometric, water-insoluble, core-shell
capsules (30 mm), where the nutritional formula is encapsulated in a gelatinous shell. Studies were carried out
to find the perfect outer liquid to encapsulate the formula and the most suitable operating conditions in terms
of spraying mode, flow rates and voltage applied to produce particles of the desired shape and size. Different
collection media to collect and suspend the produced particles were also investigated. Downstream of all the
tests, it was found out that the most suitable electrospray mode to produce 30 mm particles was the
microdripping. The outer liquid showing the highest performance was a 0.1% Sodium Alginate solution with
2% of Tween80 and 0.25% of Sodium Chloride as additives to adjust the physic-chemical properties, while the
best collection media, that was also improving the gelification reaction, was a 2% Calcium Chloride solution.
The encapsulation of the nutritional formula was achieved, however the produced particles were not as
monodisperse as expected.

The European eel (Anguilla anguilla) is a delicacy fish and an integral part of the Dutch culinary history. However, the stock of adult eel has decreased significantly due to a precipitous recruitment of glass eel fall. This relates to multiple factors including obstacles in migration pathways, loss of habitat and chemical pollution. Consequently, Anguilla anguilla has become a critically endangered species and is protected under European legislation. One possible solution, explored on laboratory scale, is the captive reproduction of eels and growth of glass eel in aquaculture. A big challenge of this technique is the limiting aspect of possible nutrients for the eels in the larval stage, as the diet must be delivered in micrometric capsules (< 20 µm) with a high protein content. Such diets are not yet available on the market. Electrohydrodynamic atomization (EHDA) is a novel option to prepare a micro-diet suitable for eel larvae. EHDA is especially interesting for its narrow size distribution capabilities and for applications which require submicrometric sizes. This project aims to evaluate the use of EHDA to produce high protein content micrometric size capsules for feeding larval eels. If successful, this would assist in the captivity production of glass eel and to make the eel culture independent of wild catches, restoring the culinary market. The project will be conducted in two phases. Firstly, tests will be conducted to evaluate the necessary conditions of the capsules using EHDA. Subsequently, the obtained capsules will be tested as feed for eel larvae. The main objective is to favour the development of a more sustainable eel culture, regarding the possibilities of investigating the current fish in natura option and exchanging it for a captivity one.