Supercritical CO₂ Extraction of Carotenoids (Astaxanthin, Adonirubin, and Adonixanthin) from Paracoccus carotinifaciens: Improved Z‐Isomer Ratio and Recovery of Carotenoids via High‐Temperature Extraction

Abstract

The effects of high-temperature supercritical CO 2 (SC-CO 2 ) extraction on Z-isomerization and recovery of carotenoids (astaxanthin, adonirubin, and adonixanthin) from Paracoccus carotinifaciens are investigated. The high-temperature extraction, especially at >100 °C, not only increases the total Z-isomer ratio of carotenoids in the resulting extracts but also improves carotenoid recovery. For example, when the SC-CO 2 extraction is performed at 60 °C and 30 MPa with an entrainer (ethanol), the total Z-isomer ratio and the recovery of astaxanthin are 11.1% and 28.4%, respectively, whereas at 120 °C, the values increase to 54.2 and 56.4%, respectively. The significant improvement in the extraction efficiency of carotenoids at high temperatures can be attributed to the increase in the ratio of carotenoid Z-isomers with high solubility in SC-CO 2 . Moreover, the effects of extraction pressure and entrainer content on Z-isomerization and recovery of carotenoids are also investigated. The results show that higher pressure and ethanol content resulted in lower Z-isomer ratios and higher recoveries of carotenoids. As the Z-isomers of carotenoids have greater bioavailability and potentially exhibit superior biological activities than the all-E-isomers, high value-added carotenoids, and higher yield can be simultaneously achieved with high-temperature extraction. Practical applications: As carotenoid extraction is usually performed using toxic organic solvents, residual solvents are a serious concern. In addition, naturally occurring carotenoids (mainly the all-E-isomers) have low bioavailability. These are important issues that need to be overcome for the industrial use of carotenoids. The Z-isomer-rich carotenoids obtained by SC-CO 2 extraction under high-temperature conditions have great potential to solve these issues simultaneously.

A review of natural astaxanthin production in a circular bioeconomy context using Paracoccus carotinifaciens

“…Honda et al, (2020a) described an efficient and ecofriendly procedure for the recovery of AXT from P. carotinifaciens using Z-isomerization-accelerating catalysts (allyl isothiocyanate at 60 • C) obtaining more than 98 % of AXT recovery. The same authors (Honda et al, 2022) evaluated the influence of supercritical CO 2 extraction + ethanol (co-solvent) on the recovery of AXT from P. carotinifaciens, achieving more than 50 % of recoveries. Recently, other classes of biocompatible solvents such as Switchable Hydrophilicity Solvent (SHS) and Deep Eutectic Solvents (DES), have been reported for the recovery of AXT from P. carotinifaciens in particular because of its low toxicity and eco-friendly nature (Sapone et al, 2022(Sapone et al, , 2021.…”