Enzymatic Processes Triggered by PEF for Astaxanthin Extraction From Xanthophyllomyces dendrorhous

Abstract

The aim of this study was to evaluate the potential of pulsed electric fields (PEF) to improve the extraction of the lipid-soluble astaxanthin from fresh biomass of a wild-type (CECT 11028) and mutant (ATCC 74219) Xanthophyllomyces dendrorhous strain using ethanol as solvent. Inactivation and propidium uptake studies revealed that inactivation is a good index for estimated the proportion of irreversible permeabilized cells when inactivation is higher than 70% in the two strains. Ethanol was ineffective for extracting carotenoids from the PEF-treated cells (20 kV/cm, 135 µs) of the two strains. However, after aqueous incubation of PEF-treated X. dendrorhous ATCC 74219 cells for 12 h, up to 2.4 ± 0.05 mg/g dried weight (d.w.) of carotenoids were extracted in ethanol. From total carotenoid extracted, around 84% corresponded to all-trans astaxanthin. The detection and quantification of esterase activity in the supernatant and the relationship between the percentage of esterase activity quantified and the amount of carotenoids extracted indicate that the extraction of astaxanthin was mediated by enzymatic esterase activity triggered by PEF during incubation. On the other hand, the formation of a large lipid globule into the cytoplasm of PEF-treated X. dendrorhous CECT 11028 cells during aqueous incubation prevented carotenoid extraction. The process developed in this investigation represents a more sustainable and greener method that those previously used for extracting astaxanthin from yeast.

Pulsed Electric Field Treatment Enhances Lipid Bioaccessibility While Preserving Oxidative Stability in Chlorella Vulgaris

“…This value is reached after 12 h of incubation for the biomass kept at either 25 • C or 37 • C. A longer incubation time (48 h) was necessary at 4 • C to yield a lipid bioaccessibility of 18.7 ± 1.6%. The reason why no further increase was reached could be that the incubation combined with PEF led to the coalescence of the lipid droplets in a large unique body, as previously shown, which was harder to access by digestive enzymes (Aguilar-Machado et al, 2020;Bensalem et al, 2018;Bodénès et al, 2016).…”

“…Hydrophilic proteins were completely released after PEF in cell wall-free mutants, while wild-type cell wall-containing cells showed three times lower protein yields. Although several studies report that PEF does not have a direct impact on the cell wall (Bensalem et al, 2018;Papachristou et al, 2020;T Lam et al, 2017), an increase in the extractability of microalgae intracellular compounds (e.g., protein, lipid, pigments, carbohydrates) by organic solvents or buffer systems after PEF treatment has been described (Aguilar-Machado et al, 2020;Buchmann et al, 2019;Kempkes et al, 2015;Silve, Kian, et al, 2018).…”

“…Expressed: PEF treatment may induce the expression of autolytic enzymes, as PEF was reported to be able to regulate gene expression (Bai et al, 2020). b. Liberated: Autolytic enzymes might be released from secretory vesicles, move through electroporated disorganized membranous systems and come in contact with the cell wall (Aguilar-Machado et al, 2020;Martínez et al, 2020).…”

Importance of Downstream Processing of Natural Astaxanthin for Pharmaceutical Application

“…This technique requires low energy expenditure, easily scalable and nonthermal, and facilitates the purification of extracted compounds since it minimizes the release of cell debris. The pulse duration and electric field strength intensity are parameters that need to be optimized for each sample since they may change with a change in the electrical conductivity and texture of the sample (Saini and Keum, 2018;Aguilar-Machado et al (2020). It has been suggested that PEF also triggers some enzyme activity, which in turn accelerates the autolysis and the subsequent release of N-ASX.…”

Post-incubation pH Impacts the Lipid Extraction Assisted by Pulsed Electric Fields from Wet Biomass of Auxenochlorella protothecoides

“…17 This enhancing effect of after-PEF incubation has been suggested to be related to an autolysis process triggered by PEF, as already reported for yeasts. 18,19 In the case of microalgae, an analogous approach was performed for the carotenoid extraction from H. pluvialis by PEF treatment combined with a 6 h post-PEF aqueous incubation. 20 The authors observed an enormous release of the esterase enzyme in the supernatant of PEFtreated suspensions in the first hours after PEF, in comparison to the untreated ones.…”