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Downstream processing of bioproducts, based on the number of purification steps involved, is the most expensive part in biotechnology and food production processes. Combination of several purification steps, including membrane filtration and electrophoresis, within a single technique is known as electrofiltration-a process based on application of electric field on a dead-end filtration system parallel to the filtrate's flow direction. In this process, biopolymers, generally charged molecules with high viscosity, undergo both electrophoretic and hydrodynamic forces, reducing the thickness of the filter cake formed. As a result, electrofiltration can reduce processing time to minutes instead of hours when using conventional filtration. The objective of the present review is to assess the possibilities to purify technically and commercially important biopolymers like poly(3-hydroxybutyrate), hyaluronic acid, chitosan and xanthan by electrofiltration.

Downstream processing of chitosan requires several technological steps that contribute to the total production costs. Precipitation and especially evaporation are energy-consuming processes, resulting in higher costs and limiting industrial scale production. This study investigated the filtration kinetics of chitosan derived from cell walls of fungi and from exoskeletons of arthropods by electrofiltration, an alternative method, thus reducing the downstream processing steps and costs. Experiments with different voltages and pressures were conducted in order to demonstrate the effect of both parameters on filtration kinetics. The concentration of the biopolymer was obtained by the average factor of 40 by applying an electric field of 4 V/mm and pressure of 4 bars. A series of analytical experiments demonstrated the lack of structural and functional changes in chitosan molecules after electrofiltration. These results, combined with the reduction of energy and processing time, define the investigated method as a promising downstream step in the chitosan production technology.

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