Optimised Production and Extraction of Astaxanthin from the Yeast Xanthophyllomyces dendrorhous

Abstract

Currently, astaxanthin demand is fulfilled by chemical synthesis using petroleum-based feedstocks. As such, alternative pathways of natural astaxanthin production attracts much research interest. This study aimed at optimising bioreactor operation parameters for astaxanthin production and evaluating strategies for its subsequent extraction. The effect of pH and agitation was evident, as a significant reduction in both biomass and astaxanthin production was observed when the culture pH was not controlled and a low agitation speed was applied. At controlled pH conditions and a high agitation speed, a significant increase in biomass (16.4 g/L) and astaxanthin production (3.6 mg/L) was obtained. Enzymatic yeast cell lysis using two commercial enzymes (Accellerase 1500 and Glucanex) was optimised using the central composite design of experiment (DoE). Accellerase 1500 led to mild cell disruption and only 9% (w/w) astaxanthin extraction. However, Glucanex treatment resulted in complete astaxanthin extractability, compared to standard extraction method (DMSO/acetone). When supercritical CO 2 was employed as an extraction solvent in Accellerase-pre-treated Xanthophyllomyces dendrorhous cells, astaxanthin extraction increased 2.5-fold. Overall, the study showed that extraction conditions can be tailored towards targeted pigments present in complex mixtures, such as in microbial cells.Microorganisms 2020, 8, 430 2 of 18 up and commercialisation of astaxanthin production [3-5], while its extraction and purification still contributes to the overall complexity and cost of the whole production process.Various cultivation modes, including batch, fed-batch, and continuous, have been investigated for carotenoid production in yeasts, either in the lab or at the pilot scale [6][7][8]. In the case of some yeast species cultivated on batch mode, high initial carbon concentrations (usually glucose) result in suppression of cell growth as well as product formation due to the Crabtree effect [9,10]. It has been demonstrated that X. dendrorhous undergoes the Crabtree effect, a phenomenon where cells metabolically switch to fermentative metabolism leading to ethanol production even under ample oxygen supply when initial glucose present is above a given threshold (strain dependent) [10,11]. Fed-batch cultivation mode is considered as an appropriate strategy to overcome such issues, as it allows the addition of one or more nutrients to the reactor during fermentation in order to maintain the concentration of the substrate below its inhibitory levels [12]. Furthermore, with regards to media optimization, low concentrations of ammonium and phosphate have been reported to be favourable towards astaxanthin production, whereas increased levels of citrate in the growth medium have been shown to stimulate astaxanthin production, as citrate can act as a carbon source towards astaxanthin biosynthesis in Phaffia rhodozyma [13]. The effect of light on astaxanthin productivity in several yeast and microalgae strains has been also extensively studied [1...

Importance of Downstream Processing of Natural Astaxanthin for Pharmaceutical Application

“…A combination of various types of enzymes, instead of just one type, acts simultaneously and leads to a more effective N-ASX release. It has been reported that the presence of β-1,3-glucanase, protease, cellulose, and pectinase gives high cell disruption and high N-ASX extraction yields in H. pluvialis and P. rhodozyma (Harith et al, 2020;Ye et al, 2020).…”

“…Although molecule degradation occurred at 80°C, the highest purity of 34% was found at this temperature at 440 bars, 80 min, without cosolvent. The use of SC-CO 2 was recently reported in P. rhodozyma by Harith et al (2020). The authors studied the effect of the temperature, pressure, and ethanol concentration as a cosolvent in enzymatic pretreated cells and found that both pressure and cosolvent concentration significantly influenced N-ASX extraction.…”

Recent Advances in Astaxanthin Micro/Nanoencapsulation to Improve Its Stability and Functionality as a Food Ingredient

“…Natural astaxanthin is extracted from synthesizing organisms and microorganisms that are cultured or collected for this purpose or extracted from by-products of the fish industry (mainly from crustaceans). Some organisms that synthesize astaxanthin are the following: microalgae ( Haematococcus pluvialis , Chlamydomonas nivalis [ 7 ], Chlorella zofingiensis [ 8 ], Neochloris wimmeri [ 9 ], Scenedesmus acutus [ 10 ]); bacteria ( Agrohacterium aurantiacum [ 11 ], Brevundimonas scallop [ 12 ], Paracoccus carotinifaciens [ 13 ]); yeasts ( Xanthophyllomyces dendrorhous [ 14 ]); Protista ( Aurantiochytrium [ 15 ]; Thraustochytrium [ 16 ]) and plants ( Adonis annua [ 17 ], Adonis aestivalis [ 18 ]). Since 1990, astaxanthin is synthetically produced and nowadays it is produced on a large scale, this being the most abundant method of production found in the world market (95% of the total) because of the lower cost of production (approximately 1000 dollars/kg) when compared with natural astaxanthin [ 5 , 19 ].…”

“…Supercritical carbon dioxide extraction has also been used to obtain astaxanthin [ 40 , 41 ]. The use of high pressure to improve the efficacy of the solvent during the extraction of astaxanthin has also been proposed [ 42 ], as well as ultrasound [ 43 ], microwave [ 44 ], magnetic-field-assisted extraction [ 45 ], pulsed electric field [ 46 ], microbial fermentation [ 14 ], and the use of enzymes [ 47 ].…”

Biological effect of astaxanthin on alcohol-induced gut damage in Carassius auratus used as experimental model

“…Xanthophyllomyces dendrorhous represent a promising choice for astaxanthin production because of the high astaxanthin yields and productivities that have been associated with this yeast (Tropea et al 2013;Gervasi et al 2020;Harith et al 2020). The cultivation of this microorganisms, through a fed-batch mode, that allow the addition of nutrients to the reactor during fermentation in order to maintain the concentration of the substrate below its inhibitory levels, have been used in this study.…”