Exploring different processes for starch extraction from microalgae and synthesis of starch-chitosan plastic films

Microalgae could become a more sustainable starch source than conventional crops. However, available refinery processes are lacking. In this study, we develop different innovative processes to refine microalgal starch and obtaining starch-based bioplastics. After lipid extraction, defatted microalgae were treated by different routes: enzymatic treatment with Alcalase; sonication in hot water or dimethyl sulfoxide (DMSO) followed by precipitation with ethanol. Enzymes allows to extract 70 % of proteins while recovering 75 % of the initial starch in the residual pellet, with a purity of 58 %. The most effective configuration based on sonication and water/DMSO extraction allowed to recover up to 80 % starch with 80-91 % purity. Chitosan improved the mechanical properties of the obtained starch-based films. The use of defatted algae or purified starch gave different properties to the films (as rigidity and water stability) showing the possibility to tailor the material characteristics depending on the biorefinery route applied.