Extraction of microalgal starch and pigments by using different cell disruption methods and aqueous two-phase system

BACKGROUND Microalgae can synthesize starch with productivity higher than conventional terrestrial crops, without the need for arable land. However, little is known about processes to extract starch from microalgae. Here, a biorefinery process is described including microalgal cell disruption followed by extraction of starch and pigments with aqueous two-phase system (ATPS) using choline chloride and polypropylene glycol 400. Sonication and bead milling were compared for cell disruption rate and starch extraction efficiency. RESULTS A first order kinetic model described well the cell disruption for both the methods, with a rate 2.6 times higher for bead milling than sonication. By applying ATPS on samples with comparable cell disruption (>93%), starch was separated better after sonication (67% recovery in the pellet) than after bead milling, for which it remained equally distributed between pellet (40%) and choline chloride phase. Pigments were extracted with 42-66% yield irrespective of the cell disruption method. Microalgal starch granules had a normal and narrow distribution for size (0.93 +/- 0.14 mu m) and a gelatinization temperature between 45-55 degrees C. CONCLUSION For the same cell disruption yield, different starch separation efficiencies can be achieved, depending on the cell disruption method applied. Although bead milling was faster than sonication in disrupting cells, it gave worst starch separation efficiency. The properties of the extracted microalgal starch indicate potential technical advantages, with respect to conventional starch sources, for applications in the bioplastic and food sector. (c) 2021 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Automated summary

A biorefinery process for extracting starch and pigments from microalgae using an aqueous two-phase system was described. Sonication was more efficient in separating starch after comparable cell disruption yield, compared to bead milling. Microalgal starch extracted had properties indicating potential technical advantages for applications in bioplastics and food sector.