Sugaring-out: A novel phase separation and extraction system

SWIEET-a salt-free alternative to QuEChERS

The efficient extraction of various analytes from a wide spectrum of matrices with organic solvents is still a great challenge in analytical chemistry. Especially polar and charged compounds are hard to extract in combination with neutral analytes of intermediate to low polarity. The QuEChERS method is often chosen and has been adapted not only to the analysis of food samples, but also to environmental matrices (soil, wastewater) or biota. In this study, we overcome major drawbacks of QuEChERS such as low recoveries of charged analytes and impairment of downstream analysis by high salt loads. The new extraction method, applicable to liquid and solid samples, is called SWIEET (sugar water isopropanol ethyl nitrile extraction technique). Phase separation of the otherwise miscible extraction solvents water and acetonitrile is achieved by sugaring-out instead of salting-out. Extraction efficiencies were greatly improved by adding isopropanol to the acetonitrile phase. The concentrations of the additives glucose and isopropanol, as well as temperature, were optimized by a design of experiment. Further improvement was achieved through electro- or double-extractions. For all sample types tested (surface water, wastewater treatment plant effluent, tomato, soil, and oats), recoveries and precision were higher with SWIEET than with the established QuEChERS method. From wastewater treatment plant effluent, 75% recovery on average were achieved with our SWIEET method compared to 37% with QuEChERS for a model analyte mixture with polarities of logDpH7 =  - 5.7 - 3.5. Higher recoveries and lower standard deviations compared to QuEChERS were achieved especially for polar and charged analytes such as metformin. Handling proved to be easy, since there was no additional solid phase and no tedious weighing of salts.

Phytochemical profiling of red raspberry (Rubus idaeus L.) honey and investigation of compounds related to its pollen occurrence

BACKGROUND

Red raspberry (Rubus idaeus L.) is an important nectar source for honey production in some specific habitats as well as an important crop, so the definition of the features of this kind of honey is noteworthy. However, due to its rarity on the market, red raspberry honey is poorly characterized. The aim of this work was the phytochemical characterization of honey containing red raspberry from different geographical origins, through melissopalynological analyses concurrently with untargeted metabolomics achieved with different chromatographic techniques coupled to mass spectrometry: solid-phase micro-extraction/gas chromatography/mass spectrometry (SPME-GC-MS) and high-performance liquid chromatography/Orbitrap mass spectrometry (HPLC-Orbitrap).

RESULTS

Only 4 out of the 12 samples involved in the study contained raspberry pollen as dominant pollen, although these honeys did not group in the hierarchical cluster analysis nor in the classical multidimensional scaling analyses used for data evaluation. The first result was the detection of mislabelling in two samples, which contained raspberry pollen only as minor or important minor pollen. Of the 188 compounds identified by HPLC-Orbitrap and of the 260 identified by SPME-GC-MS, 87 and 31 compounds were present in all samples, respectively. The structurally related compounds nicotinaldehyde and nicotinamide, nicotinic acid and nicotinyl alcohol were present in 100% of the samples and correlated with R. idaeus pollen count (r > 0.60, Pearson's correlation analysis).

CONCLUSION

This study reveals important aspects about the characterization of red raspberry honey and could give new insights on bee diet and preferences, since niacin compounds resulted interestingly to be related to the presence of red raspberry pollen. © 2024 Society of Chemical Industry.

Determination of bisphenols in beeswax based on sugaring out-assisted liquid-liquid extraction: Method development and application in survey, recycling and degradation studies

The methodology of sugaring out-assisted liquid-liquid extraction (SULLE) coupled with high-performance liquid chromatography-fluorescence detection was devised for quantifying bisphenol A (BPA) and bisphenol B (BPB) in beeswax. The effectiveness of SULLE was methodically explored and proved superior to the salting out-assisted liquid-liquid extraction approach for beeswax sample preparation. The analytical performance underwent comprehensive validation, revealing detection limits of 10 μg/kg for BPA and 20 μg/kg for BPB. The method developed was employed to analyse commercial beeswax (n = 15), beeswax foundation (n = 15) and wild-build comb wax (n = 26) samples. The analysis revealed BPA presence in four commercial beeswax samples and three beeswax foundation samples, with the highest detected residue content being 88 ± 7 μg/kg. For BPB, two beeswax foundation samples were positive, with concentrations below the limits of quantification and 85 ± 4 μg/kg, respectively. No bisphenols were detected in wild-build comb wax. Furthermore, the bisphenol removal efficacy of two recycling methods-boiling in water and methanol extraction-was assessed. The findings indicated that after four recycling cycles using water boiling, 9.6% of BPA and 29.2% of BPB remained in the beeswax. Whereas methanol extraction resulted in approximately 7% residual after one recycling process. A long-term study over 210 days revealed the slow degradation of bisphenols in comb beeswax. This degradation fitted well with a first-order model, indicating half-lives (DT50) of 139 days for BPA and 151 days for BPB, respectively. This research provides the first report on bisphenol contamination in beeswax. The low removal rate during the recycling process and the gradual degradation in beeswax underscore the significance of bisphenol contamination and migration in bee hives along with their potential risk to pollinators warranting concern. Furthermore, the developed SULLE method shows promise in preparing beeswax samples to analyse other analytes.

Formal analyses are fundamental for the definition of honey, a product representing specific territories and their changes: the case of North Tyrrhenian dunes (Italy)

Honey is a variegate matrix depending significantly on the floral origin, and it could become an important agri-food product to valorise specific territories. Being so diverse, different analytical techniques are necessary for its description. Herein we characterized the honey produced in one of the Italian sand dunes systems hosting beekeeping activities. In terms of floristic origin, phytochemical characterization, and sensory and colour analysis, honey collected in 2021 and 2022 was comparable. Honey was polyfloral, with several pollens from dune habitat plants classified as minor. The presence of the allochthonous Amorpha fruticosa L. and the ruderal Rubus fruticosus L. pollens in the category of the secondary pollens testifies the alteration of the park vegetation. The phytochemical profile was rich in polyphenols. Other interesting compounds were coumarine derivatives, likely attributable to resin-laden plants as rockroses, long chain hydroxyacids typical of royal jelly and nicotinic acid and its analogues (2-hydroxynicotinic acid and 2-hydroxyquinoline). The above-mentioned honey showed interesting features and was a good representation of the vegetation of this area. Our study pointed out the importance of relying on multiple analytical techniques for the characterization of honey and the advisability of a technical support toward beekeepers to correctly describe and valorise their product.

Lipid Recovery from Microalgae Biomass Using Sugaring-Out Extraction in Liquid Biphasic Flotation System

The increase in global temperature calls for ambitious action to reduce the release of greenhouse gases into the atmosphere. The transportation sector contributes up to 25% of the total emissions released, mainly from the burning of vehicle fuel. Therefore, scientists from all around the world are focusing on finding a sustainable alternative to conventional vehicle fuel. Biofuel has attracted much attention, as it shows great potential for the replacement of traditional fossil fuels. However, the main bottlenecks of biofuel are the ongoing controversial conflict between food security with biofuel production. Therefore, this study focuses on a sustainable extraction of lipids from microalgae for the production of biofuel using a liquid biphasic flotation system coupled with sugaring-out method. This is the first study to combine the methods of liquid biphasic flotation system with the sugaring-out technique. It represents a holistic study of optimum and effective conditions needed to extract lipids from the system and to understand the reliability of sugar solution as the agent of cell disruption. At the 15-min flotation time, 150 g/L of fructose solution with a 1:2 mass separating agent-acetonitrile ratio successfully extracted up to 74% of lipid from Chlorella sorokiniana CY-1. Two types of fatty acid methyl esters were recovered from the study, with C5:0 being the main component extracted.

Efficient analyses of triazole fungicides in water, honey and soy milk samples by popping candy-generated CO2 and sugaring-out-assisted supramolecular solvent-based microextraction prior to HPLC determinations

An enrichment method, namely popping candy-generated CO₂ and sugaring-out-assisted supramolecular solvent-based microextraction (PGS-SUPRA), was investigated for the determination of triazole fungicide residues in water, honey and soy milk samples. The extraction process was carried out by adding popping candies into a centrifuge tube. Consequently, rapid dispersion and mass transfer of extractants can be achieved without using dispersants and auxiliary devices, and therefore, the extraction efficiency increased. The extraction parameters affecting the efficiency of the developed method were investigated. The presented method was then analysed by high-performance liquid chromatography. Under the selected condition, the wide linearity of triazole fungicides after preconcentration by the proposed microextraction method ranged from 30 to 1000 μg L^-1 for triadimefon and from 90 to 1000 μg L^-1 for myclobutanil, tebuconazole and hexaconazole, with a coefficient for determination (R ²) greater than 0.992. The limits of detection (LODs) and limits of quantitation (LOQs) were in the range of 10-30 μg L^-1 and 30-90 μg L^-1, respectively. The precisions were assessed from the relative standard deviations (RSDs) of the retention time and peak area obtained from intra- (n = 3) and inter-day (n = 3 × 5) experiments, and were greater than 1.66% and 13.52%, respectively. Moreover, the proposed method provided high enhancement factors (EnFs) ranging from 14 to 51 folds. This technique has been prosperously applied for the extraction of fungicide residues in water, honey and soy milk samples with a recovery within the range of 60-114%. Overall, the developed method was found to be advantageous as compared with other sample preparation methods.

Decontamination of water co-polluted by copper, toluene and tetrahydrofuran using lauric acid

Co-contamination by organic solvents (e.g., toluene and tetrahydrofuran) and metal ions (e.g., Cu2+) is common in industrial wastewater and in industrial sites. This manuscript describes the separation of THF from water in the absence of copper ions, as well as the treatment of water co-polluted with either THF and copper, or toluene and copper. Tetrahydrofuran (THF) and water are freely miscible in the absence of lauric acid. Lauric acid separates the two solvents, as demonstrated by proton nuclear magnetic resonance (1H NMR) and Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR). The purity of the water phase separated from 3:7 (v/v) THF:water mixtures using 1 M lauric acid is ≈87%v/v. Synchrotron small angle X-Ray scattering (SAXS) indicates that lauric acid forms reverse micelles in THF, which swell in the presence of water (to host water in their interior) and ultimately lead to two free phases: 1) THF-rich and 2) water-rich. Deprotonated lauric acid (laurate ions) also induces the migration of Cu2+ ions in either THF (following separation from water) or in toluene (immiscible in water), enabling their removal from water. Laurate ions and copper ions likely interact through physical interactions (e.g., electrostatic interactions) rather than chemical bonds, as shown by ATR-FTIR. Inductively coupled plasma-optical emission spectrometry (ICP-OES) demonstrates up to 60% removal of Cu2+ ions from water co-polluted by CuSO4 or CuCl2 and toluene. While lauric acid emulsifies water and toluene in the absence of copper ions, copper salts destabilize emulsions. This is beneficial, to avoid that copper ions are re-entrained in the water phase alongside with toluene, following their migration in the toluene phase. The effect of copper ions on emulsion stability is explained based on the decreased interfacial activity and compressional rigidity of interfacial films, probed using a Langmuir trough. In wastewater treatment, lauric acid (a powder) can be mixed directly in the polluted water. In the context of groundwater remediation, lauric acid can be solubilized in canola oil to enable its injection to treat aquifers co-polluted by organic solvents and Cu2+. In this application, injectable filters obtained by injecting cationic hydroxyethylcellulose (HEC +) would impede the flow of toluene and copper ions partitioned in it, protecting downstream receptors. Co-contaminants can be subsequently extracted upstream of the filters (using pumping wells), to enable their simultaneous removal from aquifers.

Glucose as a Protein-Condensing Cellular Solute

The present study reports a surprising protein-condensing effect of glucose, prompted by our accidental observation during chemical library screening under a high-glucose condition. We noticed "glucosing-out" of certain compounds, in which physiological concentrations of glucose induced compound aggregation. Adapting the "glucosing-out" concept to proteins, our proteomic analysis identified three cellular proteins (calmodulin, rho guanine nucleotide exchange factor 40, and polyubiquitin-C) that displayed robust glucose-dependent precipitation. One of these proteins, calmodulin, formed glucose-dependent condensates that control cellular glycogenolysis in hepatic cells. Our findings suggest that glucose is a heretofore underappreciated driver of protein phase separation that may have profound effects on cellular homeostasis.

Ionic liquid-based multi-stage sugaring-out extraction of lactic acid from simulated broth and actual lignocellulosic fermentation broth

In this study, ionic liquid-based sugaring-out extraction was developed to separate lactic acid from the synthetic solution and actual lignocellulosic fermentation broth. Except for [EOHmim]BF4, the ILs with BF4- and OTF- anion can form aqueous two-phase system (ATPS) with the aid of saccharides. With the same kind of saccharides, the ATPS formation ability of ILs could be promoted by increasing the side-chain length of ILs in the order of [Hmim]BF4 ≈ [Bmim]BF4 ˃ [Emim]BF4 due to the decrease in ILs' kosmotropicity. On the other hand, for the same type of ILs, an ATPS was formed more easily with glucose than with xylose. When IL concentration varied from 35% (w/w) to 40% (w/w) at a low glucose concentration of 15% (w/w), an interesting phase reversal was observed. When lactic acid was undissociated at pH 2.0, 51.8% LA and 92.3% [Bmim]BF4 were partitioned to the top phase, and 97.0% glucose to the bottom phase using an ATPS consisting of 25% (w/w) glucose and 45% (w/w) IL. The total recovery of LA would increase to 89.0% in three-stage sugaring-out extraction from synthetic solution. In three-stage sugaring-out extraction from the filtered and unfiltered fermentation broth obtained via simultaneous saccharification and co-fermentation (SSCF) of acid-pretreated corn stover by the microbial consortium, the total recovery of LA was 89.5% and 89.8%, respectively. Furthermore, the total removal ratio of cells and pigments from the unfiltered broth was 68.4% and 65.4%, respectively. The results support IL-based sugaring-out extraction as a potential method for the recovery of lactic acid from actual fermentation broth.

Dispersive liquid-liquid microextraction method combined with sugaring-out homogeneous liquid-liquid extraction for the determination of some pesticides in molasses samples

In this study, a sensitive analytical method was developed to determine some pesticides (cyprodinil, trifloxystrobin, prometryn, propachlor, fenitrothion, chlorpyrifos, profenofos, and phosalone) in molasses samples. Pesticides were extracted from samples by dispersive liquid-liquid microextraction method combined with sugaring-out homogeneous liquid-liquid extraction and determined by gas chromatography-mass spectrometry analysis. In this method, pesticides in molasses samples were first extracted using a water-miscible solvent (acetonitrile) in the sugaring-out homogeneous liquid-liquid extraction stage. The sugar in the ratio of 84-88% naturally contained in the molasses sample enabled phase separation in the acetonitrile-water homogeneous mixture. Then acetonitrile phase containing pesticides was used as dispersing solvent in the second step of the process. Under the specified optimum conditions, the limit of detection was calculated between 0.8-6.1 ng/g and the limit of quantification was in the range of 2.5-20 ng/g. The relative standard deviation values of molasses samples containing 150 ng/g of each analyte were found to be lower than 4.9% intra-day and 5.6% for inter-day. This validated method has been successfully applied to different types of molasses.

Homogeneous liquid-liquid extraction as an alternative sample preparation technique for biomedical analysis

Liquid-liquid extraction is a widely used technique of sample preparation in biomedical analysis. In spite of the high pre-concentration capacities of liquid-liquid extraction, it suffers from a number of limitations including time and effort consumption, large organic solvent utilization, and poor performance in highly polar analytes. Homogeneous liquid-liquid extraction is an alternative sample preparation technique that overcomes some drawbacks of conventional liquid-liquid extraction, and allows employing greener organic solvents in sample treatment. In homogeneous liquid-liquid extraction, a homogeneous phase is formed between the aqueous sample and the water-miscible extractant, followed by chemically or physically induced phase separation. To form the homogeneous phase, aqueous samples are mixed with water-miscible organic solvents, water-immiscible solvents/cosolvents, surfactants, or smart polymers. Then, phase separation is induced chemically (adding salt, sugar, or buffer) or physically (changing temperature or pH). This mode is rapid, sustainable, and cost-effective in comparison with other sample preparation techniques. Moreover, homogeneous liquid-liquid extraction is more suitable for the extraction of delicate macromolecules such as enzymes, hormones, and proteins and it is more compatible with liquid chromatography with tandem mass spectrometry, which is a vital technique in metabolomics and proteomics. In this review, the principle, types, applications, automation, and technical aspects of homogeneous liquid-liquid extraction are discussed.

High-throughput subzero-temperature assisted homogenous liquid-liquid extraction for the fast sample preparation of multiple phenolic compounds in propolis

In the present study, a high-throughput homogenous liquid-liquid extraction method was developed for fast sample preparation of multiple phenolic compounds in propolis. This method was proposed based on cooling samples array in subzero temperature to induce phase separation of ACN-H₂O extractant. Due to the high-throughput ability, optimization of extraction parameters was rapidly achieved by using a 5 × 4 × 3 samples array. In addition, multiple arrays were investigated for evaluating the analytical performance of the high-throughput method, which indicated that limits of detection and quantification were ranged from 0.04 to 0.35 µg/mL and 0.12 to 1.05 µg/mL, respectively. Recoveries and precisions in inter-day high-throughput studies were in the range of 90.55-105.50% and 2.58-4.30%, respectively. Comparing with the conventional liquid extraction method, this ecofriendly high-throughput method presented remarkable advantages in reducing sample and chemical consumption, as well as saving labor and time cost. The proposed method might provide a valuable strategy for the design of high-throughput extraction procedures.

Sugaring-out induced homogeneous liquid-liquid microextraction as an alternative mode for biological sample preparation: A comparative study

Miniaturization of liquid-liquid extraction is a growing field of sample preparation to reduce solvent consumption, protect the environment, and preserve operators' health. In this work, four different modes of liquid-liquid microextraction have been compared including dispersive liquid-liquid microextraction, binary and ternary salting-out, and sugaring-out induced liquid-liquid microextraction. The extraction efficiency was evaluated by the enrichment factors of 14 different drugs from three pharmacological classes. Compared with the other modes, sugaring-out induced liquid-liquid microextraction was found to be the most efficient and, thus, it was applied for sample preparation of the antivirals in human plasma. Method optimization was performed using response surface methodology for the sugar type and amount (in mg), the sample pH, the equilibration time (in min), and the extractant volume (in µL). The method was then validated and found linear in the concentration range of 0.10-10 µg/mL for daclatasvir, 0.05-10 µg/mL for velpatasvir, and 0.20-10 µg/mL for ledipasvir, with correlation coefficients in the range 0.996-0.999. These results shows that sugaring-out induced liquid-liquid microextraction could be a more efficient microextraction mode for preparation of biological samples. Compared with other types of microextraction, sugaring-out induced liquid-liquid microextraction is greener, simpler, and cost-effective, with less tendency to affect the sample pH.

Sugaring-out extraction of erythromycin from fermentation broth

This study reports the sugaring-out extraction of erythromycin from fermentation broth using acetonitrile (ACN) as solvent and glucose as a mass separating agent. Different process parameters-glucose concentration, temperature, ACN/water ratio and pH-were optimized to achieve maximum extraction of erythromycin. 88% (w/w) of erythromycin was extracted from the model system with following optimized conditions: glucose 156.3 g/L; temperature 4 °C; ACN/water ratio 1 and pH 8.3. Further, the effect of typical fermentation media components (starch, soybean flour, CaCO3, NaCl and (NH4)2SO4) on sugaring out extraction of erythromycin was also investigated. Starch, soybean flour and CaCO3 were observed to affect erythromycin extraction only at higher concentration. Removal of suspended solids from simulated as well as real broth prior to extraction enhanced the extraction efficiency (from 72% to 87%). Sugaring out extraction of erythromycin was found to be more effective than salting out extraction. Also, higher partition coefficient was achieved in the present work than other reported methods using carbohydrates as mass separating agent. Further, it was found that the antimicrobial activity of erythromycin was preserved during sugaring out extraction of erythromycin.

Current application of electrical pre-treatment for enhanced microalgal biomolecules extraction

Pretreatment of microalgal biomass possessing rigid cell wall is a critical step for enhancing the efficiency of microalgal biorefinery. However, the conventional pretreatment processes suffer the drawbacks of complex processing steps, long processing time, low conversion efficiency and high processing costs. This significantly hinders the industrial applicability of microalgal biorefinery. The innovative electricity-aid pretreatment techniques serve as a promising processing tool to extensively enhance the release of intracellular substances from microalgae. In this review, application of electric field-based techniques and recent advances of using electrical pretreatments on microalgae cell focusing on pulsed electric field, electrolysis, high voltage electrical discharges and moderate electric field are reviewed. In addition, the emerging techniques integrating electrolysis with liquid biphasic flotation process as promising downstream approach is discussed. This review delivers broad knowledge of the present significance of the application of these methods focusing on the development of electric assisted biomolecules extraction from microalgae.

Optimization of protein extraction from Chlorella Vulgaris via novel sugaring-out assisted liquid biphasic electric flotation system

Microalgae biomass has been consumed as animal feed, fish feed and in human diet due to its high nutritional value. In this experiment, microalgae specie of Chlorella Vulgaris FSP-E was utilized for protein extraction via simple sugaring-out assisted liquid biphasic electric flotation system. The external electric force provided to the two-phase system assists in disruption of rigid microalgae cell wall and releases the contents of microalgae cell. This experiment manipulates various parameters to optimize the set-up. The liquid biphasic electric flotation set-up is compared with a control liquid biphasic flotation experiment without the electric field supply. The optimized separation efficiency of the liquid biphasic electric flotation system was 73.999 ± 0.739% and protein recovery of 69.665 ± 0.862% compared with liquid biphasic flotation, the separation efficiency was 61.584 ± 0.360% and protein recovery was 48.779 ± 0.480%. The separation efficiency and protein recovery for 5 × time scaled-up system was observed at 52.871 ± 1.236% and 73.294 ± 0.701%. The integration of simultaneous cell-disruption and protein extraction ensures high yield of protein from microalgae. This integrated method for protein extraction from microalgae demonstrated its potential and further research can lead this technology to commercialization.

Matrix-Induced Sugaring-Out: A Simple and Rapid Sample Preparation Method for the Determination of Neonicotinoid Pesticides in Honey

In the present work, we developed a simple and rapid sample preparation method for the determination of neonicotinoid pesticides in honey based on the matrix-induced sugaring-out. Since there is a high concentration of sugars in the honey matrix, the honey samples were mixed directly with acetonitrile (ACN)-water mixture to trigger the phase separation. Analytes were extracted into the upper ACN phase without additional phase separation agents and injected into the HPLC system for the analysis. Parameters of this matrix-induced sugaring-out method were systematically investigated. The optimal protocol involves 2 g honey mixed with 4 mL ACN-water mixture (v/v, 60:40). In addition, this simple sample preparation method was compared with two other ACN-water-based homogenous liquid-liquid extraction methods, including salting-out assisted liquid-liquid extraction and subzero-temperature assisted liquid-liquid extraction. The present method was fully validated, the obtained limits of detection (LODs) and limits of quantification (LOQs) were from 21 to 27 and 70 to 90 μg/kg, respectively. Average recoveries at three spiked levels were in the range of 91.49% to 97.73%. Precision expressed as relative standard deviations (RSDs) in the inter-day and intra-day analysis were all lower than 5%. Finally, the developed method was applied for the analysis of eight honey samples, results showed that none of the target neonicotinoid residues were detected.

Self-supported nickel nanoparticles on germanophosphate glasses: synthesis and applications in catalysis

The development of supported catalysts based on simple procedures without waste products and time-consuming steps is highly desirable. In this paper, self-supported nickel-based nanoparticles were obtained at the surface of the germanophosphate glasses by bottom-up process and evaluated as potential catalysts for the benzyl alcohol oxidation and bis(indolyl)methanes synthesis. A classical melt-quenching technique was used for preparing the nickel-doped germanophosphate glasses, followed by annealing under a hydrogen atmosphere at 400 °C for two different times. The approach enabled the synthesis of self-supported nanoparticles as a homogeneous film, covering the glass surface. The physical and chemical properties of synthesized glasses were characterized by UV-vis and Raman spectroscopies and thermal analysis. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were performed to monitor the growth process, morphology and chemical bonding structure of the nanoparticles surface.

Comparison of the Partition Efficiencies of Multiple Phenolic Compounds Contained in Propolis in Different Modes of Acetonitrile⁻Water-Based Homogenous Liquid⁻Liquid Extraction

Homogeneous liquid–liquid extraction (HLLE) has attracted considerable interest in the sample preparation of multi-analyte analysis. In this study, HLLEs of multiple phenolic compounds in propolis, a polyphenol-enriched resinous substance collected by honeybees, were performed for improving the understanding of the differences in partition efficiencies in four acetonitrile–water-based HLLE methods, including salting-out assisted liquid–liquid extraction (SALLE), sugaring-out assisted liquid–liquid extraction (SULLE), hydrophobic-solvent assisted liquid–liquid extraction (HSLLE), and subzero-temperature assisted liquid–liquid extraction (STLLE). Phenolic compounds were separated in reversed-phase HPLC, and the partition efficiencies in different experimental conditions were evaluated. Results showed that less-polar phenolic compounds (kaempferol and caffeic acid phenethyl ester) were highly efficiently partitioned into the upper acetonitrile (ACN) phase in all four HLLE methods. For more-polar phenolic compounds (caffeic acid, p-coumaric acid, isoferulic acid, dimethoxycinnamic acid, and cinnamic acid), increasing the concentration of ACN in the ACN–H₂O mixture could dramatically improve the partition efficiency. Moreover, results indicated that NaCl-based SALLE, HSLLE, and STLLE with ACN concentrations of 50:50 (ACN:H₂O, v/v) could be used for the selective extraction of low-polarity phenolic compounds. MgSO₄-based SALLE in the 50:50 ACN–H₂O mixture (ACN:H₂O, v/v) and the NaCl-based SALLE, SULLE, and STLLE with ACN concentrations of 70:30 (ACN:H₂O, v/v) could be used as general extraction methods for multiple phenolic compounds.

Extraction of proteins from microalgae using integrated method of sugaring-out assisted liquid biphasic flotation (LBF) and ultrasound

In this study, a simple sugaring-out supported by liquid biphasic flotation technique combined with ultrasonication was introduced for the extraction of proteins from microalgae. Sugaring-out as a phase separation method is novel and has been used in the extraction of metal ions, biomolecules and drugs. But, its functioning in protein separation from microalgae is still unknown. In this work, the feasibility of sugaring-out coupled with ultrasound for the extraction of protein was investigated. Primary studies were carried out to examine the effect of sonication on the microalgae cell as well as the separation efficiency of the integrated method. Effect of various operating parameters such as the concentration of microalgae biomass, the location of sonication probe, sonication time, ultrasonic pulse mode (includes varying ON and OFF duration of sonication), concentration of glucose, types of sugar, concentration of acetonitrile and the flow rate in the flotation system for achieving a higher separation efficiency and yield of protein were assessed. Besides, a large-scale study of the integration method was conducted to verify the consistency of the followed technique. A maximum efficiency (86.38%) and yield (93.33%) were attained at the following optimized conditions: 0.6% biomass concentration, 200 g/L of glucose concentration, 100% acetonitrile concentration with 5 min of 5 s ON/10 s OFF pulse mode and at a flow rate of 100 cc/min. The results obtained for large scale were 85.25% and 92.24% for efficiency and yield respectively. The proposed liquid biphasic flotation assisted with ultrasound for protein separation employing sugaring-out demonstrates a high production and separation efficiency and is a cost-effective solution. More importantly, this method provides the possibility of extending its application for the extraction of other important biomolecules.

Comparison of salting-out and sugaring-out liquid-liquid extraction methods for the partition of 10-hydroxy-2-decenoic acid in royal jelly and their co-extracted protein content

Homogeneous liquid-liquid extraction (h-LLE) has been receiving considerable attention as a sample preparation method due to its simple and fast partition of compounds with a wide range of polarities. To better understand the differences between the two h-LLE extraction approaches, salting-out assisted liquid-liquid extraction (SALLE) and sugaring-out assisted liquid-liquid extraction (SULLE), have been compared for the partition of 10-hydroxy-2-decenoic acid (10-HDA) from royal jelly, and for the co-extraction of proteins. Effects of the amount of phase partition agents and the concentration of acetonitrile (ACN) on the h-LLE were discussed. Results showed that partition efficiency of 10-HDA depends on the phase ratio in both SALLE and SULLE. Though the partition triggered by NaCl and glucose is less efficient than MgSO₄ in the 50% (v/v) ACN-water mixture, their extraction yields can be improved to be similar with that in MgSO₄ SALLE by increasing the initial concentration of ACN in the ACN-water mixture. The content of co-extracted protein was correlated with water concentration in the obtained upper phase. MgSO₄ showed the largest protein co-extraction at the low concentration of salt. Glucose exhibited a large protein co-extraction in the high phase ratio condition. Furthermore, NaCl with high initial ACN concentration is recommended because it produced high extraction yield for 10-HDA and the lowest amount of co-extracted protein. These observations would be valuable for the sample preparation of royal jelly.