Special Issue "Recent Advances in the Development and Application of Green Extraction Techniques"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials".

Deadline for manuscript submissions: closed (20 March 2021).

Special Issue Editors

Prof. Dr. Jaroslava Švarc-Gajić
E-Mail Website
Guest Editor
Faculty of Technology, University of Novi Sad, Bulevar cara Lazara 1, 21 000 Novi Sad, Serbia
Interests: subcritical water extraction/decomposition; green extraction techniques; biowaste valorization; bioactivity; instrumental analysis

Special Issue Information

Dear Colleagues,

In recent decades, the principles of green chemistry have been clearly encouraged and implemented to support an imperative world sustainable development. Considering an environmental protection perspective, green chemistry practitioners have been involved in the development of a plethora of convincing extraction techniques, which include but are not limited to microextraction techniques (sorptive- or solvent-based), microwave-assisted extraction, subcritical water extraction, supercritical fluid extraction, pressurized liquid extraction, ultrasonic assisted extraction, etc. Some of these techniques have become relatively mature (principally on the laboratory scale), being successfully applied to various fields, such as the environment, food industry, pharmacology, medicine, and forensic chemistry, among other strategic sectors, while others (for example, based on specifically designed green solvents or nanosorbents) are still emerging. Still, the scientific community is unanimous in concluding that their main merits are the reduction of solvent consumption and waste disposal, and extraction time, while usually, sample throughput is increased, and comparable or higher yields with higher reproducibility are reached. However, a few disadvantages are still being identified and further advances and progresses are clearly needed to widen their application. Moreover, combining several of these green techniques may help to overcome the limitations of the single technique, and synergistic results may be reached.

Thus, the goal of this Special Issue is to publish and disseminate original research data, review articles, communications, and short notes that focus on novel (experimental or theoretical) challenges, advances, and outlooks concerning the development and/or applications of green extraction methodologies.

Prof. Dr. Simone Morais
Prof. Dr. Jaroslava Švarc-Gajić
Guest Editors

Manuscript Submission Information

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Keywords

  • Advanced extraction techniques
  • Green solvents
  • Microextraction techniques
  • Microwave-assisted extraction
  • Subcritical water extraction
  • Supercritical fluid extraction
  • Pressurized liquid extraction
  • Ultrasonic-assisted extraction
  • Combined extraction techniques
  • Biological, environmental, and food applications

Published Papers (8 papers)

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Research

Article
Conventional and Enzyme-Assisted Extraction of Rosemary Leaves (Rosmarinus officinalis L.): Toward a Greener Approach to High Added-Value Extracts
Appl. Sci. 2021, 11(8), 3724; https://doi.org/10.3390/app11083724 - 20 Apr 2021
Viewed by 403
Abstract
The effect of different extraction methods of rosemary leaves on the total phenolic content (TPC), and the antioxidant activity of the extracts was herein investigated. Firstly, the solid-liquid conventional extraction (CEM) and microwave-assisted extraction (MAE) were implemented in an effort to identify the [...] Read more.
The effect of different extraction methods of rosemary leaves on the total phenolic content (TPC), and the antioxidant activity of the extracts was herein investigated. Firstly, the solid-liquid conventional extraction (CEM) and microwave-assisted extraction (MAE) were implemented in an effort to identify the effect of the solvent and of microwave irradiation on the extract quality. The extract obtained from CEM at room temperature, using ethanol/water 95:5 v/v, showed the highest antioxidant activity (IC50 = 12.1 μg/mL). MAE using ethanol/water 50:50 v/v provided an extract with TPC and DPPH radical scavenging ability in a significantly shorter extraction time (1 h for MAE and 24 h for CEM). Enzyme-assisted extraction (EAE) using five commercial enzyme formulations was implemented, and the kinetic equation was calculated. Finally, the effect of EAE as a pretreatment method to CEM was examined. Pretreatment of the plant material with pectinolytic enzymes for 1 h prior to a 24 h CEM with 50% hydroethanolic solvent was found to be the optimum conditions for the extraction of rosemary leaves, providing an extract with higher DPPH radical scavenging ability (IC50 14.3 ± 0.8 μg/mL) and TPC (15.2 ± 0.3 mgGAE/grosemary) than the corresponding extract without the enzyme pretreatment. Full article
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Article
Sustainable Biosynthesis of Antioxidants from Koji Rice Fermented with Aspergillus flavus Using Microwave-Assisted Extraction
Appl. Sci. 2021, 11(1), 430; https://doi.org/10.3390/app11010430 - 04 Jan 2021
Viewed by 533
Abstract
The present study proposes microwave-assisted extraction as a sustainable technique for the biosynthesis of bioactive compounds from rice fermented with Aspergillus flavus (koji). First, fermentation conditions (i.e., pH from 3–12, five temperatures from 20–40 °C, and four culture-fermentation media viz. wheat, wheat bran, [...] Read more.
The present study proposes microwave-assisted extraction as a sustainable technique for the biosynthesis of bioactive compounds from rice fermented with Aspergillus flavus (koji). First, fermentation conditions (i.e., pH from 3–12, five temperatures from 20–40 °C, and four culture-fermentation media viz. wheat, wheat bran, malt and rice) were optimized for producing microbial bioactive compounds. Microwave extraction was performed at 2450 MHz and 500 W for 20, 30, and 40 s with seven solvents (distilled water, ethyl acetate, hexane, ethanol, chloroform, diethyl ether, and methanol). The obtained results revealed that ethyl acetate is the most appropriate solvent for extraction. Effects of this ethyl acetate extract were compared with a commercial synthetic antioxidant. Antioxidant properties were enhanced by preventing the oxidation of the linoleic acid (C18H32O2) with an inhibition rate (antioxidant efficacy) of 73.13%. Notably, the ferrous ion binding ability was marginally lower when compared to the disodium salt of ethylenediaminetetraacetic acid (EDTA). Additionally, the obtained total content of phenolic compounds in the ethyl acetate extract of fermented rice (koji) by Aspergillus flavus was 232.11 mg based on gallic acid/mL. Antioxidant compounds in the ethyl acetate extract of fermented rice showed stability under neutral conditions, as well as at high temperatures reaching 185 °C during 2 h, but were unstable under acidic and alkaline conditions. The results demonstrate the efficacy of novel microwave-assisted extraction technique for accelerating antioxidant production during rice fermentation. Full article
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Article
Valorization Potential of Oilseed Cakes by Subcritical Water Extraction
Appl. Sci. 2020, 10(24), 8815; https://doi.org/10.3390/app10248815 - 09 Dec 2020
Cited by 1 | Viewed by 440
Abstract
The oil industry generates great quantities of oilseed cakes that remain after oil extraction. New technologies are required for their valorization, owing to their high nutritional value. Pumpkin, flax and hemp seed cakes were extracted by subcritical water under different conditions that included [...] Read more.
The oil industry generates great quantities of oilseed cakes that remain after oil extraction. New technologies are required for their valorization, owing to their high nutritional value. Pumpkin, flax and hemp seed cakes were extracted by subcritical water under different conditions that included different gas atmospheres and homogenous catalysis, and for the first time their properties were directly compared. Extracts obtained in a nitrogen atmosphere, nitrogen atmosphere with the addition of a catalyst, and carbon dioxide atmosphere were chemically and nutritionally characterised. In the aqueous extracts obtained under different extraction conditions, the content of lipids, proteins and selected minerals (calcium, potassium, sodium and phosphorus) were determined. A detailed amino acid profile was determined by chromatographic analysis. The highest relative content of essential amino acids was observed in pumpkin seed extracts (51.49 ± 0.47 to 58.58 ± 0.45 mg/100 g dry extract), whereas hemp seed extracts were the richest in flavour amino acids aspartic acid, glutamic acid and alanine. Extraction in a carbon dioxide atmosphere or in nitrogen atmosphere with a HCl modifier released generally more minerals into the aqueous phase. Aqueous oilseed cake extracts demonstrated a favorable chemical composition and great nutritional value, opening new possibilities for exploitation of this biowaste. Based on the obtained results, oilseed cake extracts obtained by subcritical water have great potential to be used for the fortification of different food products, as well as in cosmetics. Full article
Article
Mechanical Characterization of Biopolymer-Based Hydrogels Enriched with Paulownia Extracts Recovered Using a Green Technique
Appl. Sci. 2020, 10(23), 8439; https://doi.org/10.3390/app10238439 - 26 Nov 2020
Cited by 1 | Viewed by 340
Abstract
This study deals with the development and mechanical characterization of innovative starch- and gelatin-based hydrogels enriched with hydrothermal aqueous extracts from Paulownia (i.e., bark, leaves, petioles). The color, rheology, and texture properties of formulated biopolymer-based hydrogels depending on the processing conditions of the [...] Read more.
This study deals with the development and mechanical characterization of innovative starch- and gelatin-based hydrogels enriched with hydrothermal aqueous extracts from Paulownia (i.e., bark, leaves, petioles). The color, rheology, and texture properties of formulated biopolymer-based hydrogels depending on the processing conditions of the extracts was evaluated for the different Paulownia fractions. Results indicated that a clear impact on color features of the tested hydrogels was observed with the incorporation of Paulownia extracts. Rheological testing showed that weak and intermediate strength hydrogels were identified for starch- and gelatin-based hydrogels independently of used extract. A relevant softening of all gelled matrices was observed in the presence of recovered liquor extracts involving the following trend (leaves > barks > petioles). For all fractions, the highest viscoelastic features were achieved for hydrogels made with extracts recovered at 140 °C. Texture outcomes confirmed the rheological achievements. No syneresis was observed in developed hydrogels after two weeks of cold storage. Full article
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Article
Deposition Efficacy of Natural and Synthetic Antioxidants on Fabrics
Appl. Sci. 2020, 10(18), 6213; https://doi.org/10.3390/app10186213 - 07 Sep 2020
Viewed by 564
Abstract
Pine bark extracts were tested as valid natural alternatives to common phenolic antioxidants to be deposited onto solid matrices. An analytical method for determining both deposition-efficacy and maintenance of antioxidant activity on fabrics surfaces was developed and successfully applied to phenolic antioxidants and [...] Read more.
Pine bark extracts were tested as valid natural alternatives to common phenolic antioxidants to be deposited onto solid matrices. An analytical method for determining both deposition-efficacy and maintenance of antioxidant activity on fabrics surfaces was developed and successfully applied to phenolic antioxidants and pine tannins onto cotton fabric samples. Accumulated data suggest that common phenolic antioxidants and tannin contribute to an elevated antioxidant activity on fabric. A known source of odour is autoxidation of residual sebum on fabric, leading to the generation of malodourous compounds. Therefore, antioxidants hold the promise for mitigating malodour on fabrics, a top unmet consumer need around the globe. Full article
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Article
A Comparative Bio-Evaluation and Chemical Profiles of Calendula officinalis L. Extracts Prepared via Different Extraction Techniques
Appl. Sci. 2020, 10(17), 5920; https://doi.org/10.3390/app10175920 - 26 Aug 2020
Cited by 3 | Viewed by 661
Abstract
Calendula officinalis L., (marigold), well known for its medicinal properties, has been extensively studied for its therapeutic properties. Nonetheless, as far as the literature could establish, no study has attempted to comparatively assess the biological (antioxidant and enzyme inhibitory potential) of the flowers, [...] Read more.
Calendula officinalis L., (marigold), well known for its medicinal properties, has been extensively studied for its therapeutic properties. Nonetheless, as far as the literature could establish, no study has attempted to comparatively assess the biological (antioxidant and enzyme inhibitory potential) of the flowers, leaves, and roots of C. officinalis extracted using conventional (maceration and Soxhlet extraction (SE)) and non-conventional extraction (homogenizer (HAE) and ultrasound (UAE) assisted extraction) techniques. The detailed phytochemical profile of each extract along with the concentration of specific bioactive compounds has also been established. Total phenolic content was highest for the flower extracts while flavonoid content was highest in the leaf extracts. Phytochemical profiling showed that the extraction method influenced the phytochemical composition of the extract. Nicotiflorin was identified in the flower extracts only while amentoflavone occurred only in the roots, inferring that the occurrence of bioactive compounds varies within a plant. The flower extracts showed highest antioxidant potential while the roots extracts were potent inhibitors of cholinesterase and tyrosinase. This study provides valuable data on the influence of extraction techniques on the recovery of bioactive compounds from plants. In an endeavor to scale-up extraction from plant considering the more efficient extraction method is of paramount importance. Moreover, the study highlighted the necessity to thoroughly examine the biological activities of various parts of a plant obtained via different extraction protocols. Full article
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Article
Preparing High-Purity Anhydrous ScCl3 Molten Salt Using One-Step Rapid Heating Process
Appl. Sci. 2020, 10(15), 5174; https://doi.org/10.3390/app10155174 - 28 Jul 2020
Viewed by 572
Abstract
In this study, a one-step rapid heating novel process was used to prepare high-purity anhydrous scandium chloride molten salt with low-purity scandium oxide. High-purity anhydrous ScCl3 molten salt was used as the Sc-bearing raw material for preparing the Sc-bearing master alloy. Inert [...] Read more.
In this study, a one-step rapid heating novel process was used to prepare high-purity anhydrous scandium chloride molten salt with low-purity scandium oxide. High-purity anhydrous ScCl3 molten salt was used as the Sc-bearing raw material for preparing the Sc-bearing master alloy. Inert gas was used to enhance the purity of anhydrous scandium chloride and reduce the hydrolysis rate of scandium. The results show that high-purity scandium chloride (purity, 99.69%) with the scandium content of 29.61%, was obtained, and the hydrolysis rate of scandium was 1.19% under the conditions used: removing ammonium chloride; residual crystal water temperature of 400 °C; m(Sc2O3):m(NH4Cl) = 1:2.5; holding-time of 90 min; heating-rate of 12 °C/min; and argon flow of 7.5 L/min. XRD, SEM, and EPMA analyses further verified that anhydrous scandium chloride crystallization condition was relatively good and the purity of high-purity anhydrous scandium chloride approached the theory purity of anhydrous scandium chloride. Full article
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Article
Batch Stirred-Tank Green Extraction of Salvia fruticosa Mill. Polyphenols Using Newly Designed Citrate-Based Deep Eutectic Solvents and Ultrasonication Pretreatment
Appl. Sci. 2020, 10(14), 4774; https://doi.org/10.3390/app10144774 - 11 Jul 2020
Cited by 2 | Viewed by 592
Abstract
A series of citrate salts were tested as hydrogen bond acceptors to synthesize deep eutectic solvents (DES) based on lactic acid and glycerol, used as hydrogen bond donors. The DES produced were then screened to identify the highest performing system for the effective [...] Read more.
A series of citrate salts were tested as hydrogen bond acceptors to synthesize deep eutectic solvents (DES) based on lactic acid and glycerol, used as hydrogen bond donors. The DES produced were then screened to identify the highest performing system for the effective extraction of polyphenolic phytochemicals from the medicinal plant Salvia fruticosa Mill. (Greek sage). The most efficacious DES was the one composed of lactic acid and sodium citrate dibasic, at a molar ratio of 15:1 (LA-SCDB15). Furthermore, for the first time there has been evidence concerning DES pH and extraction efficiency. Using this solvent, a batch, stirred-tank extraction process was developed, by employing ultrasonication pretreatment and response surface methodology. The optimal settings determined were stirring speed 900 rpm, proportion of DES/water 77% (w/v), and ultrasonication pretreatment time 15 min. By adjusting these optimal settings, the predicted maximum total polyphenol yield was calculated to be 79.93 ± 1.92 mg gallic acid equivalents g−1 dry mass. The examination of temperature effects demonstrated that the batch, stirred-tank extraction stage was very energy-efficient, with a barrier of 7.64 kJ mol−1. Comparison of the extraction of Salvia fruticosa polyphenols with other green processes previously developed, illustrated the high extraction capacity of LA-SCDB15. The major polyphenols identified in the extracts produced under optimized settings were chlorogenic acid, luteolin 7-O-glucuronide and rosmarinic acid. Full article
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