1. Please check and comment entries here.
Table of Contents

    Topic review


    View times: 26
    Submitted by: María José Benito


    Polysaccharides from agro-food industry waste constitute one of the most important renewable resources. The great variety of their chemical composition and structure, and their biodegradability and safety make them ideal for application in diverse fields, such as the food, pharmaceutical, cosmetics, tissue engineering and biofuels industries, among others.

    1. Polysaccharides from Agricultural Waste

    Nowadays, 37 million tons of agricultural residues are generated worldwide [1] causing a serious economic and environmental problem [2]. These residues are made up of waste and plant by-products, such as skins and seeds. Plant by-products are rich sources of dietary fiber, soluble polysaccharides, phenolic compounds and fatty acids, making them particularly interesting for use as additives and functional ingredients.

    Polysaccharides from agro-food industry waste constitute one of the most important renewable resources. The great variety of their chemical composition and structure, and their biodegradability and safety make them ideal for application in diverse fields, such as the food, pharmaceutical, cosmetics, tissue engineering and biofuels industries, among others [3][4].

    Natural polysaccharides from agricultural residues form part of the plant cell walls that are highly variable in terms of structure and composition [5]. In general, cell walls are composed of high molecular weight polysaccharides, which are mainly lignin, cellulose, hemicelluloses, pectins and other non-starch polysaccharides, such as inulin and oligosaccharides [6]. Polysaccharides that form cell walls are classified as insoluble and soluble based on their ability to be soluble in water. Insoluble polysaccharides are lignin, cellulose, hemicelluloses and pectins (insoluble); the soluble polysaccharide group consists of other pectins and hemicelluloses [7].

    Composed exclusively of β-glucose molecules linked by β-1,4-glycosidic bonds, cellulose is characterized by its capacity for chemical modification and hydrophilicity [8]. Cellulose is found in different agricultural residues, such as garlic skin [9], corn [10], grape pomace [11] and carrot [12]. Cellulose has multiple applications in the food industry; among others, its application as a fat substitute [13] has been proven to improve food texture [14], and it has also been widely used as a film to protect food. [15] manufactured cellulose-based coatings from Chinese chive root extract, and the results showed that the coatings possessed antioxidant and antimicrobial properties.

    Hemicellulose is a heteropolysaccharide, composed of a heterogeneous set of polysaccharides, itself composed of two types of monosaccharides linked by β-bonds, which form a branched linear chain. It is the second most abundant component of agricultural residues, representing approximately 20–40% [16][17]. Hemicelluloses include glucans, xyloglucans, mannans, xylans and β-(1→3,1→4)-glucans [18]. However, the polysaccharides that constitute the majority of hemicelluloses are mannan and xylan [19].

    Xylan is the most abundant hemicellulose found in nature [20]. Xylan from agricultural residues can be hydrolyzed and converted into xylose; furthermore, it can be turned into xylooligosaccharides (XOS) with different degrees of polymerization [21]. Aachary and Prapulla [22] reported that XOS with a degree of polymerization of 2–3 have maximum prebiotic potential. XOS are extracted industrially from corn and sugarcane [23][24], although they can also be obtained from agricultural by-products such as pineapple rind [25], straw rice [26] and quinoa stems [27].

    Another polysaccharide that is part of the hemicelluloses is mannan, which is significantly present in agricultural residues. By enzymatic hydrolysis, mannan can be turned into mannooligosaccharides (MOS) [28]. MOS are considered as emerging prebiotics and can be obtained from different agricultural residues, such as copra flour [29].

    Pectins, mostly considered soluble fiber, are part of the cell wall of plants and are heteropolysaccharide polymers rich in polygalacturonic acid that can be composed of up to 17 different monosaccharides [30], which is why it is characterized as one of the most structurally complex natural plant polysaccharides [31]. It is composed of three structurally distinct domains: homogalacturonan (HG), rhamnogalacturonan (RG-I) and rhamnogalacturonan (RG-II).

    Pectins are traditionally obtained from agricultural by-products, such as citrus peels and apple pomace [32][33]. The increasing global demand for this heteropolysaccharide due to the numerous health benefits attributed to it [34] means that alternative sources of pectin are being sought in other vegetables and by-products, such as eggplant [35], tomato peel [36][37], broccoli stem [38] and pomegranate peel [39], among others.

    Methoxy esters, located in the C6 carboxyl groups of D-galacturonic acid, are substitutions generally found in the HG region and play an important role in the known functional properties and health benefits of these pectic polysaccharides [40]. It is composed of a repeating backbone of galacturonic acid and rhamnose disaccharide, usually with neutral side chains [41]. Although less common in the pectic fraction, RG-IIs are polysaccharides with abundant bioactive properties and many human health benefits. Their structure comprises a main chain linked to galacturonic acid and side chains of highly complex oligosaccharides and other unusual monosaccharides [42].

    In addition, depolymerization of pectin releases pectic oligosaccharides (POS) [43]. POS are currently described as emerging prebiotics with numerous health benefits [44].

    2. Extraction of Polysaccharides: Methods and Influence on the Bioactive Function

    The different extraction methods, the extraction solvent, the pH, the ratio of raw material to solvent, the temperature and the time have a significant influence on the yield, technological properties and functions of bioactive polysaccharides [45][46]. Each extraction method has its advantages and disadvantages; therefore, the extraction method chosen should be adapted to the final purpose, the nature of the by-product and the cost of the procedure.

    Table 1 shows an overview of the optimized extraction methods and their influence on the bioactive function of polysaccharides obtained from plant by-products.

    Table 1. Optimized extraction methods and their influence on the bioactive function of polysaccharides obtained from plant by-products.

    Optimized Extraction Method Compounds By-Products Influence on Bioactive Function Reference
    Hot water extraction Polysaccharides White mulberry Anti-diabetic, immunomodulatory, anti-inflammatory, antioxidant, hepatoprotective, renoprotective and anti-obesity activity; effect on gut microbiota [47]
    Hot water extraction Polysaccharides Watermelon rind Antihypertensive and antioxidant activity [48]
    Hot water extraction Polysaccharides Pomegranate fruit Prebiotic activity [49]
    Hot water extraction Polysaccharides Oleaster fruit N.d. * [50]
    Ultrasound-assisted extraction Polysaccharides/starch, pectin Yam tubers, fruit peel, tomato processing, potato… Antioxidant, anticoagulant, antitumor, anti-inflammatory and prebiotic activity [51]
    Ultrasound-assisted extraction Polysaccharides/pectin Fruit and vegetable peel: eggplant Antioxidant activity [35]
    Ultrasound-assisted extraction Polysaccharides/pectin Pomegranate peel N.d. * [52]
    Ultrasound-assisted microwave extraction Polysaccharides/pectin Tomato peel N.d. * [53]
    Ultrasound-assisted extraction Polysaccharides/pectin Custard apple peel N.d.* [54]
    Ultrasound-assisted extraction Polysaccharides/pectin Mango peel N.d. * [55]
    High hydrostatic pressure and ultrasound-assisted extraction Polysaccharides/pectin Tomato peel N.d. * [36]
    Ultrasound-assisted extraction Hemicellulose polysaccharides/xyloglycans Grape pomace N.d. * [56]
    Ultrasound-assisted extraction Fructooligosaccharides Artichoke industrial waste Prebiotic activity [57]
    Microwave-assisted extraction Polysaccharides Marshmallow roots Antioxidant, antimicrobial and antitumor activity [58]
    Microwave-assisted extraction Polysaccharides Chuanminshen violaceum root Increased antioxidant activity [59]
    Microwave-assisted extraction Polysaccharides/pectin Carica papaya L. peel N.d. * [60]
    Microwave-assisted extraction Polysaccharides Kiwifruit Antioxidant activity [61]
    Microwave-assisted extraction Polysaccharides Camptotheca acuminata fruits Antioxidant and immunomodulatory activity [62]
    Surfactant and microwave-assisted extraction Polysaccharides/pectin Orange peel N.d. * [63]
    Microwave-assisted extraction Polysaccharides Waste jamun fruit seeds N.d. * [64]
    Microwave-assisted extraction Polysaccharides Sargassum pallidum Hypoglycemic activity [65]
    Microwave-assisted extraction Polysaccharides/pectin Banana peel N.d. * [66]
    Hot-solvent microwave extraction Polysaccharides/pectin Pomelo peel N.d. * [67]
    Microwave hydrodiffusion and gravity Polysaccharides Broccoli N.d. * [68]
    Microwave-assisted extraction Polysaccharides Cocoa bean shell Antioxidant activity [69]
    Microwave-assisted extraction Polysaccharides/pectin Fruit peels N.d. * [70]
    Microwave-assisted extraction Hemicellulose polysaccharides/xyloglycans Tobacco plant residues N.d. * [71]
    Enzyme-assisted extraction Polysaccharides Fritillaria pallidiflora Schrenk Antioxidant, antimicrobial, anti-inflammatory, antitumor and antihypertensive activity [72]
    Enzyme-assisted extraction Polysaccharides Malva sylvestris plant Increased antioxidant, antitumor and antimicrobial activity [73]
    Enzyme-assisted extraction Polysaccharides Cup plant (Silphium perfoliatum L.) Antioxidant and hypoglycemic activity [74]
    Enzyme-assisted extraction Polysaccharides/pectin Kiwi pomace N.d. * [75]
    Enzyme-assisted extraction Polysaccharides/pectin Apple pomace Antioxidant and anticancer activity [76]
    Enzyme-assisted extraction Polysaccharides/pectin Pomegranate peel Antioxidant activity [77]
    Enzyme-assisted extraction Polysaccharides Dendrobium chrysotoxum Immunological activity [78]
    Enzyme-assisted supercritical fluid extraction Polysaccharides Pomegranate peel Antioxidant activity [79]
    Supercritical fluid extraction Polysaccharides Artemisia sphaerocephala Krasch. seeds N.d.* [80][81]
    Supercritical fluid extraction Polysaccharides Pomegranate peel Antioxidant activity [81]
    Deep extraction with eutectic solvent/microwave-assisted extraction Polysaccharides Bladder-wrack (Fucus vesiculosus) Antioxidant activity, cell growth inhibition [82]
    Accelerated solvent extraction Polysaccharides Bamboo shoots Antioxidant activity [83]
    Dynamic high-pressure microfluidization Polysaccharides Nelumbo nucifera leaves Antioxidant activity [84]
    Ultrasonic-cellulase synergistic extraction Polysaccharides Pineapple pomace Hypoglycemic and anticancer activity [85]
    Deep extraction with eutectic solvent Polysaccharides/pectin Pomelo peel N.d. * [86]

    * Not determined.

    HWE is one of the most widely used methods to extract polysaccharides, being conventional, simple and cheap. However, the use of HWE is limited due to its low yield; only extracellular polysaccharides can be obtained since the cell wall is not degraded [87]. High temperatures and long extraction times are needed to achieve high yields [47], which results in degradation of the structure and a decrease in quality and bioactivity [88][59]. Therefore, there is a need to explore new methods of polysaccharide extraction that ensure a good yield besides maintaining the bioactive and functional characteristics of the polysaccharides.

    UAE is based on a phenomenon called acoustic cavitation, which involves the generation and formation of gas vapor-filled bubbles in a liquid that expand and finally collapse. Cavitation generates circulating liquid currents and turbulence as well as an increase in temperature and pressure [51]. This leads to an increase in the overall extraction yield [89]. Among the advantages of UAE are that it is considered one of the most cost-effective techniques for the extraction of polysaccharides [51], apart from being efficient, fast and environmentally friendly.

    UAE has been used to extract pectic polysaccharides from the peel of fruit and vegetables, such as eggplant [35], pomegranate [52], tomato [53], custard apple [54] and mango [55]. UAE of tomato peel was able to efficiently extract two valuable bioactive ingredients (pectin and polyphenols) simultaneously, in addition to shortening the extraction time with respect to conventional extraction techniques [36]. It has also been reported that high yields of hemicellulose polysaccharides can be obtained with short extraction times, especially xyloglycans by UAE in grape pomace [56]. UAE turns out to be efficient for extracting prebiotic sugars from industrial artichoke residues: 1-kestose, nystose, fructofuranosylnystose and raffinose were successfully extracted, obtaining an extract of approximately 9.6 mg of prebiotic saccharides/g of dry raw material [57].

    MAE involves the penetration of electromagnetic radiation into a solid matrix. The heating generated is due to the molecular friction caused by the ionic conduction of the dissolved ions and the rotation of the dipoles of the polar solvent, which favor the extraction of the bioactive compounds. Both the heating produced and the internal pressure originated cause rupture of the cell; as a consequence, the structure is altered, which facilitates the release into the solvent of the bioactive compounds, improving the transfer coefficient [60][61][62]. MAE is a promising technique for polysaccharide extraction; it has advantages such as high yields, less solvent used, shorter extraction times and being environmentally friendly [63][64][65].

    Currently, MAE is widely used in the extraction of polysaccharides from various sources of by-products, such as banana peel [66], grapefruit peel [67], broccoli by-products [68] and cocoa shell [69], among others. [70] reported higher yields (18.73%) and higher purity of pectic polysaccharides extracted from fruit peels, such as dragon fruit and passion fruit, compared to conventional methods. In addition, extraction times were shortened, resulting in a reduction in energy consumption. High yields of hemicellulose polysaccharides such as xylan, glucuronoxylan and xyloxylan extracted by MAE from tobacco plant residues have also been reported [71].

    While the UAE and MAE methods break the cell wall, EAE degrades the cell parts by enzymatic hydrolysis, which causes an improvement in the yield and biological activity of polysaccharides [72][90]. The method is selective for the extracted bioactive compounds and environmentally friendly [58]. The extraction yield depends on several factors, such as the liquid–solid ratio, pH, amount of enzyme, temperature and extraction time [74][91].

    EAE has been used effectively for extraction of pectin from kiwifruit pomace, demonstrating a higher pectin yield by enzymatic extraction with Celluclast (cellulases, polygalacturonase, pectin lyase and rhamnogalacturonan lyase) than by acid extraction with citric acid [75]. [76] also reported higher extraction yields for pectin (15.3%) from apple pomace by EAE compared to acid extraction with sulfuric acid. EAE achieved higher polysaccharide extraction yields from pomegranate peel than those obtained with HWE and UAE, the extracted polysaccharides having strong antioxidant properties [77]. Extraction of polysaccharides fromDendrobium chrysotoxumby EAE provided 1.25-fold higher yields than with HWE [78].

    SFE is an emerging technology in the extraction of bioactive compounds that allows the natural qualities of the compounds to be preserved and ensures food safety [92]. The critical point of CO2(31 °C and 7.38 MPa) allows the recovery of bioactive compounds with a high degree of purity and especially useful clean extracts for functional foods [79]. SFE technology has, to a large extent, been used for apolar substances, although selective extraction of polar compounds is possible by using modifications. [80] reported a yield of 18.59% for SFE of polysaccharides fromArtemisia sphaerocephalaplants with extraction parameters of 45 MPa at 45 °C, with a CO2flow of 20 L/h for 2 h. Rivas et al.

    New polysaccharide extraction methods are being developed, such as deep extraction with eutectic solvents [82], accelerated extraction with solvents [83][86] and high-pressure dynamic microfluidization [84]. In addition, the previously mentioned methods are also combined to improve the yields and bioactive functions of polysaccharides.

    The polysaccharides, mannose, rhamnose, glucose, galactose, xylose, arabinose, fucose, glucuronic acid and galacturonic acid, were extracted from pineapple pomace by combining UAE and EAE to provide ultrasonic-cellulase synergistic extraction; the extracted polysaccharides demonstrated the ability to inhibit development of HepG2 cells resistant to insulin and therefore can be considered potential ingredients to develop a new beneficial food [85]. In addition, Liew et al. [86] reported a 1.5 to 3.5 times higher yield for the extraction of pectic polysaccharides combining UAE and EAE compared to separate extraction methods.

    The entry is from 10.3390/ijerph18115937


    1. FAOSTAT. FAO Database. Available online: (accessed on 23 December 2020).
    2. Wang, B.; Dong, F.; Chen, M.; Zhu, J.; Tan, J.; Fu, X.; Wang, Y.; Chen, S. Advances in recycling and utilization of agricultural wastes in China: Based on environmental risk, crucial pathways, influencing factors, policy mechanism. Procedia Environ. Sci. 2016, 31, 12–17.
    3. Chen, C.; Zhang, B.; Huang, Q.; Fu, X.; Liu, R.H. Microwave-assisted extraction of polysaccharides from Moringa oleifera Lam. leaves: Characterization and hypoglycemic activity. Ind. Crops Prod. 2017, 100, 1–11.
    4. Santagata, G.; Mallardo, S.; Fasulo, G.; Lavermicocca, P.; Valerio, F.; Di Biase, M.; Di Stasio, M.; Malinconico, M.; Volpe, M.G. Pectin-honey coating as novel dehydrating bioactive agent for cut fruit: Enhancement of the functional properties of coated dried fruits. Food Chem. 2018, 258, 104–110.
    5. Maity, P.; Nandi, A.K.; Manna, D.K.; Pattanayak, M.; Sen, I.K.; Bhanja, S.K.; Samanta, S.; Panda, B.C.; Paloi, S.; Acharia, K.; et al. Structural characterization and antioxidant activity of a glucan from Meripilus giganteus. Carbohydr. Polym. 2017, 157, 1237–1245.
    6. Zhao, J.L.; Zhang, M.; Zhou, H.L. Microwave-assisted extraction, purification, partial characterization, and bioactivity of polysaccharides from Panax ginseng. Molecules 2019, 24, 1605.
    7. Flanagan, B.M.; Williams, B.A.; Sonni, F.; Mikkelsen, D.; Gidley, M.J. Fruit and vegetable insoluble dietary fibre in vitro fermentation characteristics depend on cell wall type. Bioact. Carbohydr. Diet. Fibre 2020, 23, 100223.
    8. He, X.; Lu, W.; Sun, C.; Khalesi, H.; Mata, A.; Andaleeb, R.; Fang, Y. Cellulose and cellulose derivatives: Different colloidal states and food-related applications. Carbohydr. Polym. 2021, 255, 117334.
    9. Hernández-Varela, J.D.; Chanona-Pérez, J.J.; Benavides, H.A.C.; Sodi, F.C.; Vicente-Flores, M. Effect of ball milling on cellulose nanoparticles structure obtained from garlic and agave waste. Carbohydr. Polym. 2021, 255, 117347.
    10. Gu, H.; Gao, X.; Zhang, H.; Chen, K.; Peng, L. Fabrication and characterization of cellulose nanoparticles from maize stalk pith via ultrasonic-mediated cationic etherification. Ultrason. Sonochem. 2020, 66, 104932.
    11. Coelho, C.C.; Michelin, M.; Cerqueira, M.A.; Gonçalves, C.; Tonon, R.V.; Pastrana, L.M.; Freitas-Silva, O.; Vicente, A.A.; Cabral, L.M.C.; Teixeira, J.A. Cellulose nanocrystals from grape pomace: Production, properties and cytotoxicity assessment. Carbohydr. Polym. 2018, 192, 327–336.
    12. Siqueira, G.; Oksman, K.; Tadokoro, S.K.; Mathew, A.P. Re-dispersible carrot nanofibers with high mechanical properties and reinforcing capacity for use in composite materials. Compos. Sci. Technol. 2016, 123, 49–56.
    13. Espert, M.; Wiking, L.; Salvador, A.; Sanz, T. Reduced-fat spreads based on anhydrous milk fat and cellulose ethers. Food Hydrocoll. 2020, 99, 105330.
    14. Wang, Y.; Wang, W.; Jia, H.; Gao, G.; Wang, X.; Zhang, X.; Wang, Y. Using cellulose nanofibers and its palm oil Pickering emulsion as fat substitutes in emulsified sausage. J. Food Sci. 2018, 83, 1740–1747.
    15. Riaz, A.; Lagnika, C.; Luo, H.; Nie, M.; Dai, Z.; Liu, C.; Abdin, M.; Hashim, M.M.; Li, D.; Song, J. Effect of Chinese chives (Allium tuberosum) addition to carboxymethyl cellulose based food packaging films. Carbohydr. Polym. 2020, 235, 115944.
    16. Tatar, F.; Tunç, M.T.; Dervisoglu, M.; Cekmecelioglu, D.; Kahyaoglu, T. Evaluation of hemicellulose as a coating material with gum arabic for food microencapsulation. Food Res. Int. 2014, 57, 168–175.
    17. Yang, H.; Yi, N.; Zhao, S.; Qaseem, M.F.; Zheng, B.; Li, H.; Feng, J.-X.; Wu, A.-M. Characterization of hemicelluloses in sugarcane (Saccharum spp. hybrids) culm during xylogenesis. Int. J. Biol. Macromol. 2020, 165, 1119–1128.
    18. Scheller, H.V.; Ulvskov, P. Hemicelluloses. Ann. Rev. Plant Biol. 2020, 61, 263–289.
    19. Naidu, D.S.; Hlangothi, S.P.; John, M.J. Bio-based products from xylan: A review. Carbohydr. Polym. 2018, 179, 28–41.
    20. Fu, G.Q.; Zhang, S.C.; Chen, G.G.; Hao, X.; Bian, J.; Peng, F. Xylan-based hydrogels for potential skin care application. Int. J. Biol. Macromol. 2020, 158, 244–250.
    21. Ratnadewi, A.A.I.; Handayani, W.; Oktavianawati, I.; Santoso, A.B.; Puspaningsih, N.N.T. Isolation and hydrolysis xylan from soybean waste with endo-β-1, 4-D-xilanase of Bacillus sp. from soil termite abdomen. Agric. Agric. Sci. Procedia 2016, 9, 371–377.
    22. Aachary, A.A.; Prapulla, S.G. Xylooligosaccharides (XOS) as an emerging prebiotic: Microbial synthesis, utilization, structural characterization, bioactive properties, and applications. Compr. Rev. Food Sci. Food Saf. 2011, 10, 2–16.
    23. Monteiro, C.R.; Avila, P.F.; Pereira, M.A.F.; Pereira, G.N.; Bordignon, S.E.; Zanella, E.; Stambuk, B.U.; de Oliveira, D.; Goldbeck, R.; Poletto, P. Hydrothermal treatment on depolymerization of hemicellulose of mango seed shell for the production of xylooligosaccharides. Carbohydr. Polym. 2021, 253, 117274.
    24. Wu, Q.; Fan, G.; Yu, T.; Sun, B.; Tang, H.; Teng, C.; Yang, R.; Li, X. Biochemical characteristics of the mutant xylanase T-XynC (122) C (166) and production of xylooligosaccharides from corncobs. Ind. Crops Prod. 2019, 142, 111848.
    25. Banerjee, S.; Patti, A.F.; Ranganathan, V.; Arora, A. Hemicellulose based biorefinery from pineapple peel waste: Xylan extraction and its conversion into xylooligosaccharides. Food Bioprod. Process. 2019, 117, 38–50.
    26. Gautério, G.V.; da Silva, L.G.G.; Hübner, T.; da Rosa Ribeiro, T.; Kalil, S.J. Maximization of xylanase production by Aureobasidium pullulans using a by-product of rice grain milling as xylan source. Biocatal. Agric. Biotechnol. 2020, 23, 101511.
    27. Gil-Ramirez, A.; Salas-Veizaga, D.M.; Grey, C.; Karlsson, E.N.; Rodriguez-Meizoso, I.; Linares-Pastén, J.A. Integrated process for sequential extraction of saponins, xylan and cellulose from quinoa stalks (Chenopodium quinoa Willd.). Ind. Crops Prod. 2018, 121, 54–65.
    28. Jana, U.K.; Suryawanshi, R.K.; Prajapati, B.P.; Soni, H.; Kango, N. Production optimization and characterization of mannooligosaccharide generating β-mannanase from Aspergillus oryzae. Bioresour. Technol. 2018, 268, 308–314.
    29. Jana, U.K.; Kango, N. Characteristics and bioactive properties of mannooligosaccharides derived from agro-waste mannans. Int. J. Biol. Macromol. 2020, 149, 931–940.
    30. Chan, S.Y.; Choo, W.S.; Young, D.J.; Loh, X.J. Pectin as a rheology modifier: Origin, structure, commercial production and rheology. Carbohydr. Polym. 2017, 161, 118–139.
    31. Mohnen, D. Pectin structure and biosynthesis. Curr. Opin. Plant Biol. 2008, 11, 266–277.
    32. Elshahed, M.S.; Miron, A.; Aprotosoaie, A.C.; Farag, M.A. Pectin in diet: Interactions with the human microbiome, role in gut homeostasis, and nutrient-drug interactions. Carbohydr. Polym. 2020, 255, 117388.
    33. Putnik, P.; Bursać Kovačević, D.; Režek Jambrak, A.; Barba, F.J.; Cravotto, G.; Binello, A.; Lorenzo, J.M.; Shpigelman, A. Innovative “green” and novel strategies for the extraction of bioactive added value compounds from citrus wastes—A review. Molecules 2017, 22, 680.
    34. Bayar, N.; Friji, M.; Kammoun, R. Optimization of enzymatic extraction of pectin from Opuntia ficus indica cladodes after mucilage removal. Food Chem. 2018, 241, 127–134.
    35. Kazemi, M.; Khodaiyan, F.; Hosseini, S.S. Utilization of food processing wastes of eggplant as a high potential pectin source and characterization of extracted pectin. Food Chem. 2019, 294, 339–346.
    36. Grassino, A.N.; Ostojić, J.; Miletić, V.; Djaković, S.; Bosiljkov, T.; Zorić, Z.; Ježek, D.; Rimac Brnčić, S.; Brnčić, M. Application of high hydrostatic pressure and ultrasound-assisted extractions as a novel approach for pectin and polyphenols recovery from tomato peel waste. Innov. Food Sci. Emerg. Technol. 2020, 64, 102424.
    37. Halambek, J.; Cindrić, I.; Grassino, A.N. Evaluation of pectin isolated from tomato peel waste as natural tin corrosion inhibitor in sodium chloride/acetic acid solution. Carbohydr. Polym. 2020, 234, 115940.
    38. Petkowicz, C.L.; Williams, P.A. Pectins from food waste: Characterization and functional properties of a pectin extracted from broccoli stalk. Food Hydrocoll. 2020, 107, 105930.
    39. Shakhmatov, E.G.; Makarova, E.N.; Belyy, V.A. Structural studies of biologically active pectin-containing polysaccharides of pomegranate Punica granatum. Int. J. Biol. Macromol. 2019, 122, 29–36.
    40. Fishman, M.L.; Chau, H.K.; Qi, P.X.; Hotchkiss, A.T.; Garcia, R.A.; Cooke, P.H. Characterization of the global structure of low methoxyl pectin in solution. Food Hydrocoll. 2015, 46, 153–159.
    41. Wu, D.; Zheng, J.; Hu, W.; Zheng, X.; He, Q.; Linhardt, R.J.; Ye, X.; Chen, S. Structure-activity relationship of citrus segment membrane RG-I pectin against galectin-3: The galactan is not the only important factor. Carbohydr. Polym. 2020, 245, 116526.
    42. Park, H.R.; Park, S.B.; Hong, H.D.; Suh, H.J.; Shin, K.S. Structural elucidation of anti-metastatic rhamnogalacturonan II from the pectinase digest of citrus peels (Citrus unshiu). Int. J. Biol. Macromol. 2017, 94, 161–169.
    43. Sabater, C.; Blanco-Doval, A.; Margolles, A.; Corzo, N.; Montilla, A. Artichoke pectic oligosaccharide characterisation and virtual screening of prebiotic properties using in silico colonic fermentation. Carbohydr. Polym. 2020, 255, 117367.
    44. Chung, W.S.F.; Meijerink, M.; Zeuner, B.; Holck, J.; Louis, P.; Meyer, A.S.; Wells, J.M.; Flint, H.J.; Duncan, S.H. Prebiotic potential of pectin and pectic oligosaccharides to promote anti-inflammatory commensal bacteria in the human colon. FEMS Microbiol. Ecol. 2017, 93, fix127.
    45. Fang, J.; Wang, Z.; Wang, P.; Wang, M. Extraction, structure and bioactivities of the polysaccharides from Ginkgo biloba: A review. Int. J. Biol. Macromol. 2020, 162, 1897–1905.
    46. Shang, H.; Chen, S.; Li, R.; Zhou, H.; Wu, H.; Song, H. Influences of extraction methods on physicochemical characteristics and activities of Astragalus cicer L. polysaccharides. Process Biochem. 2018, 73, 220–227.
    47. He, X.; Fang, J.; Ruan, Y.; Wang, X.; Sun, Y.; Wu, N.; Zhao, Z.; Chang, Y.; Ning, N.; Guo, H.; et al. Structures, bioactivities and future prospective of polysaccharides from Morus alba (white mulberry): A review. Food Chem. 2018, 245, 899–910.
    48. Romdhane, M.B.; Haddar, A.; Ghazala, I.; Jeddou, K.B.; Helbert, C.B.; Ellouz-Chaabouni, S. Optimization of polysaccharides extraction from watermelon rinds: Structure, functional and biological activities. Food Chem. 2017, 216, 355–364.
    49. Khatib, M.; Giuliani, C.; Rossi, F.; Adessi, A.; Al-Tamimi, A.; Mazzola, G.; Di Gioia, D.; Innocenti, M.; Mulinacci, N. Polysaccharides from by-products of the Wonderful and Laffan pomegranate varieties: New insight into extraction and characterization. Food Chem. 2017, 235, 58–66.
    50. Sharifian-Nejad, M.S.; Shekarchizadeh, H. Physicochemical and functional properties of oleaster (Elaeagnus angustifolia L.) polysaccharides extracted under optimal conditions. Int. J. Biol. Macromol. 2019, 124, 946–954.
    51. Cui, R.; Zhu, F. Ultrasound modified polysaccharides: A review of structure, physicochemical properties, biological activities and food applications. Trends Food Sci. Technol. 2020, 107, 491–508.
    52. Moorthy, I.G.; Maran, J.P.; Muneeswari, S.; Naganyashree, S.; Shivamathi, C.S. Response surface optimization of ultrasound assisted extraction of pectin from pomegranate peel. Int. J. Biol. Macromol. 2015, 72, 1323–1328.
    53. Sengar, A.S.; Rawson, A.; Muthiah, M.; Kalakandan, S.K. Comparison of different ultrasound assisted extraction techniques for pectin from tomato processing waste. Ultrason. Sonochem. 2020, 61, 104812.
    54. Shivamathi, C.S.; Moorthy, I.G.; Kumar, R.V.; Soosai, M.R.; Maran, J.P.; Kumar, R.S.; Varalakshmi, P. Optimization of ultrasound assisted extraction of pectin from custard apple peel: Potential and new source. Carbohydr. Polym. 2019, 225, 115240.
    55. Guandalini, B.B.V.; Rodrigues, N.P.; Marczak, L.D.F. Sequential extraction of phenolics and pectin from mango peel assisted by ultrasound. Food Res. Int. 2019, 119, 455–461.
    56. Minjares-Fuentes, R.; Femenia, A.; Garau, M.C.; Candelas-Cadillo, M.G.; Simal, S.; Rosselló, C. Ultrasound-assisted extraction of hemicelluloses from grape pomace using response surface methodology. Carbohydr. Polym. 2016, 138, 180–191.
    57. Machado, M.T.; Eca, K.S.; Vieira, G.S.; Menegalli, F.C.; Martínez, J.; Hubinger, M.D. Prebiotic oligosaccharides from artichoke industrial waste: Evaluation of different extraction methods. Ind. Crops Prod. 2015, 76, 141–148.
    58. Hashemifesharaki, R.; Xanthakis, E.; Altintas, Z.; Guo, Y.; Gharibzahedi, S.M.T. Microwave-assisted extraction of polysaccharides from the marshmallow roots: Optimization, purification, structure, and bioactivity. Carbohydr. Polym. 2020, 240, 116301.
    59. Dong, H.; Lin, S.; Zhang, Q.; Chen, H.; Lan, W.; Li, H.; He, J.; Qin, W. Effect of extraction methods on the properties and antioxidant activities of Chuanminshen violaceum polysaccharides. Int. J. Biol. Macromol. 2016, 93, 179–185.
    60. Maran, J.P.; Prakash, K.A. Process variables influence on microwave assisted extraction of pectin from waste Carcia papaya L. peel. Int. J. Biol. Macromol. 2015, 73, 202–206.
    61. Han, Q.H.; Liu, W.; Li, H.Y.; He, J.L.; Guo, H.; Lin, S.; Zhao, L.; Chen, H.; Liu, Y.-W.; Wu, D.-T.; et al. Extraction optimization, physicochemical characteristics, and antioxidant activities of polysaccharides from kiwifruit (Actinidia chinensis Planch.). Molecules 2019, 24, 461.
    62. Hu, W.; Zhao, Y.; Yang, Y.; Zhang, H.; Ding, C.; Hu, C.; Zhou, L.; Zhang, Z.; Yuan, S.; Chen, Y.; et al. Microwave-assisted extraction, physicochemical characterization and bioactivity of polysaccharides from Camptotheca acuminata fruits. Int. J. Biol. Macromol. 2019, 133, 127–136.
    63. Su, D.; Li, P.; Quek, S.Y.; Huang, Z.; Yuan, J.; Li, G.; Shan, Y. Efficient extraction and characterization of pectin from orange peel by a combined surfactant and microwave assisted process. Food Chem. 2019, 286, 1–7.
    64. Al-Dhabi, N.A.; Ponmurugan, K. Microwave assisted extraction and characterization of polysaccharide from waste jamun fruit seeds. Int. J. Biol. Macromol. 2020, 152, 1157–1163.
    65. Cao, C.; Huang, Q.; Zhang, B.; Li, C.; Fu, X. Physicochemical characterization and in vitro hypoglycemic activities of polysaccharides from Sargassum pallidum by microwave-assisted aqueous two-phase extraction. Int. J. Biol. Macromol. 2018, 109, 357–368.
    66. Swamy, G.J.; Muthukumarappan, K. Optimization of continuous and intermittent microwave extraction of pectin from banana peels. Food Chem. 2017, 220, 108–114.
    67. Chen, Q.; Hu, Z.; Yao, F.Y.D.; Liang, H. Study of two-stage microwave extraction of essential oil and pectin from pomelo peels. LWT Food Sci. Technol. 2016, 66, 538–545.
    68. Ferreira, S.S.; Passos, C.P.; Cardoso, S.M.; Wessel, D.F.; Coimbra, M.A. Microwave assisted dehydration of broccoli by-products and simultaneous extraction of bioactive compounds. Food Chem. 2018, 246, 386–393.
    69. Mellinas, A.C.; Jiménez, A.; Garrigós, M.C. Optimization of microwave-assisted extraction of cocoa bean shell waste and evaluation of its antioxidant, physicochemical and functional properties. LWT 2020, 127, 109361.
    70. Dao, T.A.T.; Webb, H.K.; Malherbe, F. Optimisation of pectin extraction from fruit peels by response surface method: Conventional versus microwave-assisted heating. Food Hydrocoll. 2021, 113, 106475.
    71. Yuan, Y.; Zou, P.; Zhou, J.; Geng, Y.; Fan, J.; Clark, J.; Li, Y.; Zhang, C. Microwave-assisted hydrothermal extraction of non-structural carbohydrates and hemicelluloses from tobacco biomass. Carbohydr. Polym. 2019, 223, 115043.
    72. Abuduwaili, A.; Rozi, P.; Mutailifu, P.; Gao, Y.; Nuerxiati, R.; Aisa, H.A.; Yili, A. Effects of different extraction techniques on physicochemical properties and biological activities of polysaccharides from Fritillaria pallidiflora Schrenk. Process Biochem. 2019, 83, 189–197.
    73. Rostami, H.; Gharibzahedi, S.M.T. Cellulase-assisted extraction of polysaccharides from Malva sylvestris: Process optimization and potential functionalities. Int. J. Biol. Macromol. 2017, 101, 196–206.
    74. Guo, Y.; Shang, H.; Zhao, J.; Zhang, H.; Chen, S. Enzyme-assisted extraction of a cup plant (Silphium perfoliatum L.) polysaccharide and its antioxidant and hypoglycemic activities. Process Biochem. 2020, 92, 17–28.
    75. Yuliarti, O.; Goh, K.K.; Matia-Merino, L.; Mawson, J.; Brennan, C. Extraction and characterisation of pomace pectin from gold kiwifruit (Actinidia chinensis). Food Chem. 2015, 187, 290–296.
    76. Wikiera, A.; Mika, M.; Starzyńska-Janiszewska, A.; Stodolak, B. Application of Celluclast 1.5 L in apple pectin extraction. Carbohydr. Polym. 2015, 134, 251–257.
    77. Li, Y.; Zhu, C.P.; Zhai, X.C.; Zhang, Y.; Duan, Z.; Sun, J.R. Optimization of enzyme assisted extraction of polysaccharides from pomegranate peel by response surface methodology and their anti-oxidant potential. Chin. Herb. Med. 2018, 10, 416–423.
    78. Pan, L.H.; Wang, J.; Ye, X.Q.; Zha, X.Q.; Luo, J.P. Enzyme-assisted extraction of polysaccharides from Dendrobium chrysotoxum and its functional properties and immunomodulatory activity. LWT Food Sci. Technol. 2015, 60, 1149–1154.
    79. Mushtaq, M.; Sultana, B.; Anwar, F.; Adnan, A.; Rizvi, S.S.H. Enzyme-assisted supercritical fluid extraction of phenolic antioxidants from pomegranate peel. J. Supercrit. Fluids 2017, 104, 122–131.
    80. Chen, J.; Li, J.; Sun, A.D.; Zhang, B.L.; Qin, S.G.; Zhang, Y.Q. Supercritical CO2 extraction and pre-column derivatization of polysaccharides from Artemisia sphaerocephala Krasch. seeds via gas chromatography. Ind. Crops Prod. 2014, 60, 138–143.
    81. Rivas, M.Á.; Casquete, R.; de Guía Córdoba, M.; Benito, M.J.; Hernández, A.; Ruiz-Moyano, S.; Martín, A. Functional properties of extracts and residual dietary fibre from pomegranate (Punica granatum L.) peel obtained with different supercritical fluid conditions. LWT 2021, 145, 111305.
    82. Shang, X.C.; Chu, D.; Zhang, J.X.; Zheng, Y.F.; Li, Y. Microwave-assisted extraction, partial purification and biological activity in vitro of polysaccharides from bladder-wrack (Fucus vesiculosus) by using deep eutectic solvents. Sep. Purif. Technol. 2020, 259, 118169.
    83. Chen, G.; Chen, K.; Zhang, R.; Chen, X.; Hu, P.; Kan, J. Polysaccharides from bamboo shoots processing by-products: New insight into extraction and characterization. Food Chem. 2018, 245, 1113–1123.
    84. Zhang, L.; Tu, Z.C.; Wang, H.; Kou, Y.; Wen, Q.H.; Fu, Z.F.; Chang, H.X. Response surface optimization and physicochemical properties of polysaccharides from Nelumbo nucifera leaves. Int. J. Biol. Macromol. 2015, 74, 103–110.
    85. Hu, H.; Zhao, Q.; Xie, J.; Sun, D. Polysaccharides from pineapple pomace: New insight into ultrasonic-cellulase synergistic extraction and hypoglycemic activities. Int. J. Biol. Macromol. 2019, 121, 1213–1226.
    86. Liew, S.Q.; Ngoh, G.C.; Yusoff, R. Teoh, W.H. Acid and deep eutectic solvent (DES) extraction of pectin from pomelo (Citrus grandis (L.) Osbeck) peels. Biocatal. Agric. Biotechnol. 2018, 13, 1–11.
    87. Mohan, K.; Muralisankar, T.; Uthayakumar, V.; Chandirasekar, R.; Revathi, N.; Abirami, R.G.; Velmurugan, K.; Sathishkumar, P.; Jayakumar, R.; Seedevi, P. Trends in the extraction, purification, characterisation and biological activities of polysaccharides from tropical and sub-tropical fruits-A comprehensive review. Carbohydr. Polym. 2020, 238, 116185.
    88. Gharibzahedi, S.M.T.; Smith, B.; Guo, Y. Pectin extraction from common fig skin by different methods: The physicochemical, rheological, functional, and structural evaluations. Int. J. Biol. Macromol. 2019, 136, 275–283.
    89. Tomke, P.D.; Zhao, X.; Chiplunkar, P.P.; Xu, B.; Wang, H.; Silva, C.; Rathod, V.K.; Cavaco-Paulo, A. Lipase-ultrasound assisted synthesis of polyesters. Ultrason. Sonochem. 2017, 38, 496–502.
    90. Nadar, S.S.; Rao, P.; Rathod, V.K. Enzyme assisted extraction of biomolecules as an approach to novel extraction technology: A review. Food Res. Int. 2018, 108, 309–330.
    91. Poojary, M.M.; Orlien, V.; Passamonti, P.; Olsen, K. Enzyme-assisted extraction enhancing the umami taste amino acids recovery from several cultivated mushrooms. Food Chem. 2017, 234, 236–244.
    92. Da Silva, R.P.F.F.; Rocha-Santos, T.A.P.; Duarte, A.C. Supercritical fluid extraction of bioactive compounds. TrAC Trends Anal. Chem. 2016, 76, 40–51.