Enhanced extraction of astaxanthin using aqueous biphasic systems composed of ionic liquids and potassium phosphate

UPLC-QTOF-MS-based metabolomics and chemometrics studies of geographically diverse C. torulosa needles

Cupressus torulosa, an evergreen tree commonly known as the Himalayan or Bhutan cypress, is a significant coniferous species native to the Himalayan regions of Bhutan, northern India, Nepal, and Tibet. In this study, we employed ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) integrated with chemometrics to analyze the metabolite profiles of C. torulosa needles collected from 14 distinct geographical regions. Advanced statistical tools, including Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), were utilized to identify significant variations in the chemical composition across these locations. Our analysis identified 24 marker compounds consistently present in all samples, screened using stringent filtering criteria including One-way ANOVA, moderated T-test, and multiple testing correction with the Benjamini-Hochberg FDR method. Additionally, for the first time, we established the flavonoid biosynthesis pathway in C. torulosa, enhancing the understanding of its metabolic fingerprint. These findings provide critical insights into the phytochemical diversity of C. torulosa and offer valuable tools for quality control, authentication and advancing the application of UPLC-QTOF-MS in natural product research.

Aqueous two-phase systems - versatile and advanced (bio)process engineering tools

Aqueous two-phase systems (ATPS), also known as Aqueous Biphasic Systems (ABS), have been extensively studied as platforms for the separation and purification of biomolecules and other valuable compounds. These liquid-liquid extraction (LLE) systems have been a tool for biotechnology since its origin (Albertsson, 1950's), recently expanding to exciting fields such as health, biomedicine and material sciences. Due to their biocompatibility, amenability, flexibility, and versatility, ATPS have been applied across various research areas, addressing many challenges associated with conventional methodologies. In this feature article, we first discuss the fundamentals of ATPS and the molecular mechanisms that govern their formation and are crucial for their application. We then explore the most prominent and innovative applications of these systems in downstream processing. Additionally, we provide insights into the design of in situ upstream-downstream integrated platforms, and their use as pre-treatment and analytical tools. The latest advancements in ATPS applications within disruptive bioengineering and biotechnology fields are presented, along with their pioneering use in emerging scientific areas, such as the formation of all-aqueous (water-in-water) emulsions, microfluidic systems, and membrane-free batteries. Overall, this work underscores the transformative potential of ATPS in various branches of science, pinpointing directions for future research to fully explore and maximize ATPS capabilities, overcome existing hurdles, and drive innovation forward.

Enhancement of Lithium-Mediated Nitrogen Reduction by Modifying Center Atom of Tetraalkyl-Type Ionic Liquids

The lithium-mediated nitrogen reduction reaction (Li-NRR) offers a viable alternative to the Haber-Bosch process for ammonia production. However, ethanol, a common proton carrier in Li-NRR, exhibits electrochemical instability, leading to oxidation at the anode or byproduct formation at the cathode. This study replaces alcoholic proton carriers with ionic liquids (ILs), specifically tetrabutylphosphonium chloride (TBPCl) and tetrabutylammonium chloride (TBACl), to examine how the electronegativity differences between the central atom and adjacent carbon of the cation affect catalytic performance. The results show that switching the central atom in tetraalkyl-type ILs markedly enhances performance, specifically resulting in a 1.45-fold increase in Faradaic efficiency (FE) with the transition from phosphonium to ammonium cation of ILs. Additionally, optimal IL concentrations in the electrolyte are identified to maximize ammonia yield. TBACl, in particular, demonstrates enhanced ammonia production and operational stability, achieving an ammonia yield rate of 13.60 nmol/cm2/s, an FE of 39.5 %, and operational stability for over 12 h under conditions of 10 mA/cm2 and 10 atm. This research underscores the potential of precise IL modifications for more efficient and sustainable Li-NRR.

Recent Advances in Astaxanthin as an Antioxidant in Food Applications

In recent years, astaxanthin as a natural substance has received widespread attention for its potential to replace traditional synthetic antioxidants and because its antioxidant activity exceeds that of similar substances. Based on this, this review introduces the specific forms of astaxanthin currently used as an antioxidant in foods, both in its naturally occurring forms and in artificially added forms involving technologies such as emulsion, microcapsule, film, nano liposome and nano particle, aiming to improve its stability, dispersion and bioavailability in complex food systems. In addition, research progress on the application of astaxanthin in various food products, such as whole grains, seafood and poultry products, is summarized. In view of the characteristics of astaxanthin, such as insolubility in water and sensitivity to light, heat, oxygen and humidity, the main research trends of astaxanthin-loaded systems with high encapsulation efficiency, good stability, good taste masking effect and cost-effectiveness are also pointed out. Finally, the possible sensory effects of adding astaxanthin to food aresummarized, providing theoretical support for the development of astaxanthin-related food.

Techniques for recovery and recycling of ionic liquids: A review

Due to beneficial properties like non-flammability, thermal stability, low melting point and low vapor pressure, ionic liquids (ILs) have gained great interest from engineers and researchers in the past decades to replace conventional solvents. The superior characteristics of ILs make them promising for applications in fields as wide-ranging as pharmaceuticals, foods, nanoparticles synthesis, catalysis, electrochemistry and so on. To alleviate the high cost and environmental impact of ILs, various technologies have been reported to recover and purify the used ILs, as well as recycling the ILs. The aim of this article is to overview the state-of-the-art research on the recovery and recycling technologies for ILs including membrane technology, distillation, extraction, aqueous two-phase system (ATPS) and adsorption. In addition, challenges and future perspectives on ILs recovery are discussed. This review is expected to provide valuable insights for developing effective and environmentally friendly recovery methods for ILs.

Extraction and separation of astaxanthin with the help of pre-treatment of Haematococcus pluvialis microalgae biomass using aqueous two-phase systems based on deep eutectic solvents

The microalgae Haematococcus pluvialis are the main source of the natural antioxidant astaxanthin. However, the effective extraction of astaxanthin from these microalgae remains a significant challenge due to the rigid, non-hydrolyzable cell walls. Energy savings and high-efficiency cell disruption are essential steps in the recovery of the antioxidant astaxanthin from the cysts of H. pluvialis. In the present study, H. pluvialis microalgae were first cultured in Bold's Basal medium under certain conditions to reach the maximum biomass concentration, and then light shock was applied for astaxanthin accumulation. The cells were initially green and oval, with two flagella. As the induction time increases, the motile cells lose their flagellum and become red cysts with thick cell walls. Pre-treatment of aqueous two-phase systems based on deep eutectic solvents was used to decompose the cell wall. These systems included dipotassium hydrogen phosphate salt, water, and two types of deep eutectic solvents (choline chloride-urea and choline chloride-glucose). The results of pre-treatment of Haematococcus cells by the studied systems showed that intact, healthy cysts were significantly ruptured, disrupted, and facilitated the release of cytoplasmic components, thus facilitating the subsequent separation of astaxanthin by liquid-liquid extraction. The system containing the deep eutectic solvent of choline chloride-urea was the most effective system for cell wall degradation, which resulted in the highest ability to extract astaxanthin. More than 99% of astaxanthin was extracted from Haematococcus under mild conditions (35% deep eutectic solvent, 30% dipotassium hydrogen phosphate at 50 °C, pH = 7.5, followed by liquid-liquid extraction at 25 °C). The present study shows that the pre-treatment of two-phase systems based on deep eutectic solvent and, thus, liquid-liquid extraction is an efficient and environmentally friendly process to improve astaxanthin from the microalgae H. pluvialis.

Tailor-made solvents for microbial carotenoids recovery

In recent years, microbial carotenoids have emerged as a promising alternative for the pharmaceutical and food industries, particularly in promoting human health due to their potent antioxidant and antimicrobial properties. Microbial carotenoids, particularly those produced by yeast, bacteria, and microalgae, are synthesized intracellularly, requiring the use of solvents for their effective extraction and recovery. The conventional use of toxic volatile organic solvents (VOCs) like hexane, petroleum ether, and dimethyl sulfoxide in the extraction of microbial carotenoids has been common. However, ongoing research is introducing innovative, non-toxic, environmentally friendly tailor-made solvents, such as ionic liquids (IL) and deep eutectic solvents (DES), indicating a new era of cleaner and biocompatible technologies. This review aims to highlight recent advancements in utilizing IL and DES for obtaining carotenoids from microorganisms. Additionally, we explore the utilization of in silico tools designed to determine the solubilities of microbial carotenoids in tailor-made DES and ILs. This presents a promising alternative for the scientific community, potentially reducing the need for extensive experimental screening of solvents for the recovery of microbial carotenoids in the separation processing. According to our expert perspective, both IL and DES exhibit a plethora of exceptional attributes for the recovery of microbial carotenoids. Nevertheless, the current employment of these solvents for recovery of carotenoids is restricted to scientific exploration, as their feasibility for practical application in industrial settings has yet to be conclusively demonstrated. KEY POINTS: • ILs and DES share many tailoring properties for the recovery of microbial carotenoids • The use of ILs and DES for microbial carotenoid extraction remains driven by scientific curiosity. • The economic feasibility of ILs and DES is yet to be demonstrated in industrial applications.

Selectively extraction of astaxanthin from Haematococcus pluvialis by aqueous biphasic systems composed of ionic liquids and deep eutectic solutions

Haematococcus pluvialis is rich in astaxanthin ester (Ast1) and free astaxanthin (Ast2). The astaxanthin is natural antioxidant, and shows higher biodegradability and eco-friendly characteristics than commercial astaxanthin. However, the existing extraction technology is difficult to achieve selectively separation of Ast1 and Ast2. Novel aqueous biphasic systems (ABSs) composed of ionic liquids (ILs) and deep eutectic solvents (DESs) were developed to selectively extract Ast1 and Ast2. The results showed that the ABS composed of tributyloctylphosphine chloride ([P4448]Cl) and choline chloride:d-fructose ([ChCl][Fru]) performed best. The yield and partition coefficient of astaxanthin was 2.35 mg·g-1 and 103.59, respectively. Moreover, Ast1 and Ast2 could be selectively separately with the highest coefficient of specificity of 48.31. Furthermore, the ABS maintained an excellent extraction capacity after three cycles of recycling. As compared with organic solvent extraction and prior methods, the IL-DES ABS is more efficient, recyclable, and environmentally friendly for selectively extraction of astaxanthin.

pH-responsive switchable deep eutectic solvents to mediate pretreatment method for trace analysis of triazole fungicides in peel wastes

The existing QuEChERS-combined analytical pretreatment methods are limited by large reagent consumption, high environmental burden, and mediocre effects. To provide an efficient and green pretreatment method, this study developed pH-responsive switchable deep eutectic solvents (SDESs) to extract triazole fungicides (TFs) from fruit peel wastes, which could enhance the preconcentration effect of target compounds in food waste samples with complex matrices. The mechanisms of pH-induced phase transition and hydrophobicity-hydrophilicity conversion of pH-responsive SDESs were investigated by pH phase diagrams and chemical characterization techniques, respectively. We validated the established method by high-performance liquid chromatography-diode array detector (HPLC-DAD), and lower LOD (0.089-0.351 ng mL^-1), LOQ (0.297-1.172 ng mL^-1), RSD (≤8.8 %) and satisfactory recoveries (90.6 %-110.9 %) and preconcentration factors (389-512) were obtained in rotting grape peel, watermelon peel, and orange peel samples. Our findings highlight the potential of pH-responsive SDESs in the extraction and analysis of various natural food products.

Removal of Fluoride from Aqueous Solution Using Shrimp Shell Residue as a Biosorbent after Astaxanthin Recovery

Natural astaxanthin has been widely used in the food, cosmetic, and medicine industries due to its exceptional biological activity. Shrimp shell is one of the primary natural biological sources of astaxanthin. However, after astaxanthin recovery, there is still a lot of chitin contained in the residues. In this study, the residue from shrimp (Penaeus vannamei) shells after astaxanthin extraction using ionic liquid (IL) 1-ethyl-3-methyl-imidazolium acetate ([Emim]Ac) was used as a bioadsorbent to remove fluoride from the aqueous solution. The results show the IL extraction conditions, including the solid/liquid ratio, temperature, time, and particle size, all played important roles in the removal of fluoride by the shrimp shell residue. The shrimp shells treated using [Emim]Ac at 100 °C for 2 h exhibited an obvious porous structure, and the porosity showed a positive linear correlation with defluorination (DF, %). Moreover, the adsorption process of fluoride was nonspontaneous and endothermic, which fits well with both the pseudo-second-order and Langmuir models. The maximum adsorption capacity calculated according to the Langmuir model is 3.29 mg/g, which is better than most bioadsorbents. This study provides a low-cost and efficient method for the preparation of adsorbents from shrimp processing waste to remove fluoride from wastewater.

Solubility and Stability of Carotenoids in Ammonium- and Phosphonium-Based Ionic Liquids: Effect of Solvent Nature, Temperature and Water

Ionic liquids (ILs) have arisen as alternatives to organic solvents and been used in natural pigment extraction in recent decades. However, the solubility and stability of carotenoids in phosphonium- and ammonium-based ILs are insufficiently explored. In this work, the physicochemical properties of the ILs, and the dissolution behavior and storage stability of three carotenoids (astaxanthin, β-carotene, and lutein) in the IL aqueous solution were investigated. The results showed that the solubility of the carotenoids in the acidic IL solution is higher than that in the alkaline IL solution, and the optimal pH is about 6. The solubility of astaxanthin (40 mg/100 g), β-carotene (105 mg/100 g), and lutein (5250 mg/100 g) was the highest in tributyloctylphosphonium chloride ([P₄₄₄₈]Cl) due to the van der Waals forces with [P₄₄₄₈]⁺ and hydrogen bonding with Cl^-. A high temperature was beneficial to improve the solubility, but it can reduce the storage stability. Water has no significant effect on the carotenoid stability, but a high water content decreases the carotenoid solubility. A IL water content of 10-20%, an extraction temperature of 338.15 K, and a storage temperature of less than 298.15 K are beneficial for reducing the IL viscosity, improving carotenoid solubility, and maintaining good stability. Moreover, a linear correlation was found between the color parameters and carotenoid contents. This study provides some guidance for screening suitable solvents for carotenoid extraction and storage.

Aqueous Two-Phase Systems Based on Ionic Liquids and Deep Eutectic Solvents as a Tool for the Recovery of Non-Protein Bioactive Compounds—A Review

Aqueous two-phase systems (ATPS) based on ionic liquids (IL) and deep eutectic solvents (DES) are ecofriendly choices and can be used to selectively separate compounds of interest, such as bioactive compounds. Bioactive compounds are nutrients and nonnutrients of animal, plant, and microbial origin that benefit the human body in addition to their classic nutritional properties. They can also be used for technical purposes in food and as active components in the chemical and pharmaceutical industries. Because they are usually present in complex matrices and low concentrations, it is necessary to separate them in order to increase their availability and stability, and ATPS is a highlighted technique for this purpose. This review demonstrates the application of ATPS based on IL and DES as a tool for recovering nonprotein bioactive compounds, considering critical factors, results and the most recent advances in this field. In addition, the review emphasizes the perspectives for expanding the use of nonconventional ATPS in purification systems, which consider the use of molecular modelling to predict experimental conditions, the investigation of diverse compounds in phase-forming systems, the establishment of optimal operational parameters, and the verification of bioactivities after the purification process.

Influence of the Use of an Ionic Liquid as Pre-Hydrodistillation Maceration Medium on the Composition and Yield of Cannabis sativa L. Essential Oil

Cannabis sativa L. is a multi-purpose crop, whose resilience, adaptability and soil-enriching properties make it a low-impact production. In the last years, the cultivation of the "industrial" hemp varieties (THC < 0.2%) has been promoted by many Countries, opening a whole new market of hemp-derived products, such as its essential oil (EO). Its distillation might represent an effective method to exploit a residue of the hemp fiber production (flowers), complying with the guidelines of the circular economy. In the present work, different concentrations of an ionic liquid (IL; 1,3-dimethyl-1H-imidazol-3-ium dimethylphosphate) have been studied as a pre-hydrodistillation maceration medium. The EO yields have been evaluated, and their compositions have been analyzed by GC-EIMS. The use of 100% and 90% IL concentrations gave a hydrodistillation yield increment of 250% and 200%, respectively. The 200% yield increase was maintained when the 100% IL was recycled after the hydrodistillation. The lower IL concentrations incremented the cannabinoid and oxygenated sesquiterpene contents, while the opposite was true for sesquiterpene hydrocarbons. The proposed IL-enhanced hydrodistillation medium applied to hemp, studied for the first time in the present work, might be used to both (i) noteworthy increment the hydrodistillation yield and (ii) modulate the obtained EO composition based on the desired final product.

Enhanced recovery of astaxanthin from recombinant Kluyveromyces marxianus with ultrasonication-assisted alcohol/salt aqueous biphasic system

Microbial astaxanthin with strong antioxidant activity is greatly demanded for diverse applications. Extractive disruption in aqueous biphasic system (ABS) integrates the cells disruption and biomolecules recovery processes in one-step operation, allowing the direct recovery of intracellular biomolecules with biphasic system upon released from cells. In this study, astaxanthin was recovered from recombinant Kluyveromyces marxianus yeast cells via extractive disruption using alcohol/salt ABS. Recombinant K. marxianus yeast is engineered to produce high concentration of free form astaxanthin. Highest partition coefficient (K = 90.02 ± 2.25) and yield (Y = 96.80% ± 0.05) of astaxanthin were obtained with ABS composed of 20% (w/w) 1-propanol and 20% (w/w) sodium citrate of pH 5, 0.5% (w/w) yeast cells loading and additional of 1% (w/w) 1-butyl-3-methylimidazolium tetrafluoroborate (Bmim)BF₄ to improve the migration of astaxanthin to alcohol-rich top phase. The incorporation of 2.5 h of ultrasonication to the biphasic system further enhanced the astaxanthin recovery in ABS. The direct recovery of astaxanthin from recombinant K. marxianus cells was demonstrated with the ultrasonication-assisted alcohol/salt ABS which integrates the extraction and concentration of astaxanthin in a single-step operation.

Current developments on the application of microbial carotenoids as an alternative to synthetic pigments

Microbial carotenoids have attracted rising interest from several industries as a sustainable alternative to substitute the synthetic ones. Traditionally, carotenoids available in the market are obtained by the chemical route using nonrenewable sources (petrochemicals), revealing the negative impact on the environment and consumers. The most promising developments in the upstream and downstream processes of microbial carotenoids are reviewed in this work. The use of agro-based raw materials for bioproduction, and alternative solvents such as biosolvents, deep eutectic solvents, and ionic liquids for the recovery/polishing of microbial carotenoids were also reviewed. The principal advances in the field, regarding the biorefinery and circular economy concepts, were also discussed for a better understanding of the current developments. This review provides comprehensive overview of the hot topics in the field besides an exhaustive analysis of the main advantages/drawbacks and opportunities regarding the implementation of microbial carotenoids in the market.

Recovery of astaxanthin from shrimp (Penaeus vannamei) waste by ultrasonic-assisted extraction using ionic liquid-in-water microemulsions

In this study, an ultrasonic-assisted extraction using microemulsions was developed for the recovery of natural astaxanthin from shrimp waste. To select applicable solvent systems, the phase equilibrium, microstructure, and physical properties of the microemulsions were investigated. Then the effect of ultrasonic power, ultrasonic time, and microemulsion composition on the extraction efficiency (EEAst) and extraction yield (EAst) of astaxanthin were determined. Compared with organic solvents (ethanol, acetone, and dimethyl sulfoxide), the microemulsion contained tributyloctylphosphonium bromide ([P4448]Br), tributyloctylphosphonium trifluoroacetate ([P4448]CF3COO), or tetrabutylphosphonium trifluoroacetate ([P4444]CF3COO) resulted in significantly enhanced extraction of astaxanthin due to the stronger electrostatic interactions and hydrogen-bonding interactions. When ultrasonic-assisted extraction conditions were 50 W and 60 min, the highest EEAst and EAst reached 32.47 µg·g-1 and 99% by using the IL-in-water microemulsion of [P4448]Br/(TX-100 + n-butanol)/water (0.13:0.25:0.62, w/w), respectively. The IL-based microemulsion is an adequate alternative to conventional methods in the extraction and recovery of astaxanthin from natural bioresources.