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

Abstract

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 ∼m) and a gelatinization temperature between 45-55 °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.

Microalgae Biorefinery: Optimization of Starch Recovery for Bioplastic Production

“…Cultivation experiments performed in this study were designed based on results obtained in a previous study. 28 Based on these data, we could predict that starting from an inoculum of 0.3 g L −1 , N would be depleted after 1 day. After N depletion, all CO 2 uptake is directed toward the accumulation of reserve compounds (starch and lipids), since without nitrogen cells cannot synthesize new functional biomass as proteins and nucleic acids.…”

“…The extracts were analyzed for pigment concentration as described previously. 28 The pellet was then dried under a fume hood at environmental temperature. The experiment was carried out in duplicate.…”

“…Starch mass was quantified by means of selective enzymatic hydrolysis by using a "total starch assay kit" (Megazyme, ref K-TSTA, Ireland), following the protocol previously described. 28,31 The recovery yield of starch (η starch ) in the obtained pellets was calculated by eq 5…”

“…26−28 By using ATPS, starch was recovered in the interface or in the pellet phase, with an yield between 67 and 79%. 26,28 However, the reported purity of refined starch obtained was not higher than 50% 28 and no application was tested. The aim of this work is to contribute to the development of a biorefinery to obtain starch from microalgae to be used for the production of plastic films.…”

Starch/PVOH aqueous solutions: a chemical–physical characterization

“…Moreover, the structural properties of starch extracted from microalgae exceed those of corn starch. In 2021, Di Caprio et al 22 performed the extraction of starch from a strain of the microalga Tetradesmus obliquus (generally known as Scenedesmus obliquus ), finding that the gelatinization temperature and the average size of the starch granules are lower than in traditional starch sources.…”