Assessing the main opportunities used of biomass, biowaste from forestry, agro-industrial or food-industrial residues into high-value-added products associated with green solvents
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Valorisation of biomass and food-related wastes including extraction of value-added compounds from these sources represent a dynamically developed area of research and technology. Substantial research activity has been focused on the new types of extraction and refining processes during the last decades. In the presence of green solvents such as deep eutectic solvents (DESs), naturally deep eutectic solvents (NADESs), and low-transition temperature mixtures (LTTMs) the interest for the recovery of new products and bioactive compounds usable as additives and functional ingredients in industrial food sector with the aim to enhance food quality has been renewed and reinforced. DESs, NADES, and LTTMS are attractive solvents for the deconstruction/fractionation (or pretreatment) of biomass and modification of cellulose. The scope of this study consists in identifying the nutritional and nutraceutical potential of raw by-products, and in using possible processes for the production of individual compounds by separation, fractionation, and extraction. Another section is oriented on the application green solvents for fractionation of biomass or delignification/modification of pulp, and their valorisation for the product of added value (fibres, cellulose nanofibrils, cellulose nanocrystals). Acknowledgement This work was supported by the Slovak Research and Development Agency under the contracts No. APVV-15-0052, APVV-0393-14, APVV-16-0088 and VEGA grant 1/0403/19.
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Assessing the main opportunities used of biomass, biowaste from forestry, agro-industrial or food-industrial residues into high-value-added products associated with green solvents
- 1. Assessing the main opportunities used of biomass, biowaste from forestry, agro- industrial or food-industrial residues into high-value-added products associated with green solvents Michal Jablonsky* – Ales Haz Department of Wood, Pulp, and Paper, Institute of Natural and Synthetic Polymers, Slovak University of Technology, Radlinského 9, 81237 Bratislava, Slovak Republic * michal.jablonsky@stuba.sk
- 2. D. I. Mendeleey „burning petroleum as fuel would be akin to firing up a kitchen stove with bank notes"
- 3. Challenge • biowaste is a unique source of raw materials • Simple and clean fractionation of the main components of biowaste represents a very important step in the field of clean renewable carbon economy • new efficient methods or pre-treatment / fractionation / extraction methods
- 4. Green solvents • 12 principles of green chemistry • Deep eutectic solvents • Natural deep eutectic solvents • Low-transition temperature mixtures • Low-melting mixtures
- 5. Basic physical/chemical properties of deep eutectic solvents • Density • Viscosity • Conductivity • Acido-basic properties • Refractive index • Thermal stability
- 6. Density vs. temperature Fig. 1: Temperature dependence of density for investigated DESs: ■LacA/alanine (9:1); ●LacA/Gly (9:1); ▲LacA/Bet (1:2); ▼ChCl/LacA (1:9); ★ChCl/LacA (1:10); ◀ChCl/EG (1:2); ▹ChCl/CitA·H2O (2:1); □ChCl/LacA (1:5); ○ChCl/GlycA (1:3); △ChCl/Gly (1:2); ▿ChCl/OxA·2H2O (1:1), ✰MaA/Suc/water (1:1:2.8); ×ChCl/MaA (1:1); ▶ChCl/CitA·H2O (1:1); ◃ChCl/U (1:2); ✴ChCl/LacA (1:1) (Škulcová, 2018a). 20 30 40 50 60 70 80 1100 1150 1200 1250 1300 1350 (kgm -3 ) T (°C)
- 7. Viscosity Fig. 2: Temperature dependence of viscosity of investigated DESs: ■LacA/alanine (9:1); ●LacA/glycine (9:1); ▲LacA/Bet (1:2); ▼ChCl/LacA (1:9); ★ChCl/LacA (1:10); ◀ChCl/EG (1:2); ▹ChCl/CitA·H2O (2:1); □ChCl/LacA (1:5); ○ChCl/GlycA (1:3); △ChCl/Gly (1:2); ▿ChCl/OxA·2H2O (1:1); ✰MaA/Suc: water (1:1:2.8); ×ChCl/MaA (1:1) (Škulcová, 2018a) 20 30 40 50 60 70 80 90 0 100 200 300 400 500 (mPas) T (°C)
- 8. Acido-basic properties of deep eutectic solvents DES Molar ratio pH [0.5 mol L−1] pH [1.0 mol L−1] LacA/Alan 9:1 2.17 2.54 LacA/Gly 9:1 2.26 2.49 LacA/Bet 1:2 2.45 2.43 ChCl/LacA 1:9 1.64 1.66 ChCl/LacA 1:10 1.73 1.89 ChCl/EG 1:2 4.36 4.20 ChCl/CitA·H2O 2:1 1.34 1.15 ChCl/LacA 1:5 1.67 1.85 ChCl/GlycA 1:3 1.29 1.80 ChCl/Gly 1:2 4.44 4.50 ChCl/OxA·2H2O 1:1 1.20 0.97 Suc/MaA/water 1:1:2.8 2.05 1.94 ChCl/MaA 1:1 1.60 NA ChCl/CitA·H2O 1:1 1.70 2.23 ChCl/LacA 1:1 2.07 1.65 Tab. 1: Values of pH for aqueous solutions of selected DESs with concentration 0.5 mol L−1 or 1.0 mol L−1 at 23 ± 2 °C (Škulcová, 2018a)
- 9. Thermal stability DES 60 °C 80 °C 100 °C 120 °C Weight loss of sample, in % ChCl/MalA 5.98 6.44 37.67 35.48 ChCl/LacA 4.83 7.85 12.50 17.47 ChCl/TartA 3.48 4.77 4.82 9.39 Tab. 2: Weight loss of investigated DESs after 10 hours at different temperature (Škulcová et al., 2017b) * Deviation for all measurements < 1.5% Tolerable weight loss for the DESs happens at 80 °C.
- 10. • analytical chemistry -separation and detection techniques • removal of pollutants from different processes • isolation and fractionation different compounds from native biomass and waste • preparation of biofuels • electrochemistry • catalysis, organic syntheses • ... Application areas
- 11. Extraction of added value compounds • Extraction of flavonoids • Extraction of polyphenols • Extraction of other compounds
- 12. Plant-based sources Extracted bioactive compounds Sophora japonica flavonoids Equisetum palustre polyphenols Radix scutellariae hydroxysafflor yellow A Dittany cartormin Fennel carthamin Marjoram oleacein Mint oleocanthal Sage phenolic acids Carthamus cintorius genistin Virgin olive oil genistein Locinerae japonicae apigenin Cajanus cajan leaves -mangostin Pigeon pea roots tanshinone Garcinia mangostana crytotanshinone Chamaecyparis obtusa tanshinone II A; terpenoid Tab. 3: Illustrative list of value-added bioactive compounds extracted by metal-free Type III DESs and sources of the compounds (Jablonsky and Sima, 2019; Zainal-Abidin et al. 2017; Bah et al., 2013; Kamarudin et al., 2017; García et al., 2016; Teixeira et al. 2014).
- 13. Tab. 3: Illustrative list of value-added bioactive compounds extracted by metal-free Type III DESs and sources of the compounds Plant-based sources Extracted bioactive compounds Salvia miltiorrhiza bunge proteins Seaweed carrageenan Algae proteins, lipids, acids Spruce bark polyphenols Animal-based sources Cod skin collagen peptides Bovine blood bovine serum albumin, proteins Bird feathers keratin Food residues-based sources Olive oil phenolic compounds Palm oil tocols (tocopherols, tocotrienols) Grape skins and wine lees flavonoids, anthocyanins
- 14. Tab. 4: Extracted value added compounds and their sources, composition of DESs used for extraction of these compounds, and biological activity of extracted compounds (Jablonsky et al., 2018, Jablonsky and Sima, 2019). Substrate Solvents Extracted value added compounds and their biological activities or function Ref. Dittany, fennel, majoram, mint, sage LacA/NH4Ac; ChCl/LacA; LacA/glycine/water; LacA/NaAc Polyphenols (dietary and cosmetic supplements, Ayurveda - traditional medicine); flavonoids (anti- allergic, anti-inflammatory, anti-oxidant, anti- microbial, anti-cancer) Bakirtzi et al., 2016 Chamaecy-paris obtusa ChCl/Bu-diol Myricetin (anti-tumor); amentoflavone (anti- malarial activity, anti-cancer activity) Bi et al., 2013 Grape skins ChCl/Gly; ChCl/OxA; ChCl/Sor; ChCl/MaA; ChCl:Prol:MaA Flavonoids; pharmacological activities (anti- allergic, anti-inflammatory, anti-oxidant, anti- cancer, anti-diarrheal) Bubalo et al., 2016 Artemisia annua leaves [N(Me)(Oc)3]Cl/EG; [N(Me)(Oc)3]Cl/Pr-OH; [N(Me)(Oc)3]Cl/Pr-diol; [N(Me)(Oc)3]Cl/Gly[N(Me)(Oc)3]Cl/Bu-OH; [N(Me)(Oc)3]Cl /Bu-diol; [N(Me)(Oc)3]Cl/hexyl alcohol; [N(Me)(Oc)3]Cl /capryl alcohol; [N(Me)(Oc)3]Cl /decyl alcohol; [N(Me)(Oc)3]Cl /dodecyl alcohol; [N(Me)(Oc)3]Cl /cyclohexanol; [N(Me)(Oc)3]Cl /menthol; [N(Me)(Oc)3]Cl/Bu-OH Artemisinin; anti-parasitic (malaria) Cao et al., 2017a Pigeon pea roots ChCl/1,6-hexanediol Genistin, genistein (antiatherosclerotic, estrogenic, anticancer and antiviral effects); apigenin (chemopreventive role, anti-renal, stimulant of adult neurogenesis, prevention of Alzheimer’s disease) Cui et al., 2015 Carthamus tinctorius LacA/Glu; Prol/MaA; ChCl/Suc; Hydroxysafflor yellow (cerebro vascular, cardio vascular treatment); cartormin and carthamin (modulation of central nervous system, cardiovascular functions, anti-coagulative, anti- inflammatory, anti-oxidant, hepatoprotective, antihypertensive, anti-tumor activity); flavonoids Dai et al., 2013b
- 15. Substrate Solvents Extracted value added compounds and their biological activities or function Ref. Catharanthus roseus ChCl/Pr-diol; LacA/Glu; Prol/MaA; ChCl/MaA; ChCl/Glu; Glu/Fru/Suc Food additives, anti-tumor, anti-oxidant, anti cardiovascular disease, anti aging and neurological disease, anti inflammation, anti diabetes, anti-bacterial infection Dai et al., 2016 Berberidis Radix, Epimedii Folium, Notoginseng Radix et Rhizoma, Rhei Rhizoma et Radix, and Salviae Miltiorrhizae Radix et Rhizoma ChCl/Glu; ChCl/maltose; ChCl/Suc; ChCl/xylitol; ChCl/sorbitol; ChCl/EG; ChCl/Gly; ChCl/CitA; ChCl/LevA; ChCl/OxA; ChCl/LacA; ChCl/MaA; ChCl/malonate; ChCl/U 1:2; ChCl/1-MeU; ChCl/Me2U; ChCl/acetamide; Bet/Glu; Bet/maltose; Bet/Suc; Bet/xylitol; Bet/sorbitol; Bet/EG; Bet/Gly; Bet/CitA; Bet/LevA; Bet/LacA; Bet/MaA; Bet/U; Bet/MeU; Prol/Glu; Prol/Suc; Prol/sorbitol; Prol/Gly; Prol/CitA; Prol/LevA; Prol/OxA; Prol/LacA; Prol/MaA; Prol/malonate; Prol/U; Prol/MeU; Prol/acetamide Alkaloids (anti-malaria, anti-asthma, anti-cancer, cholinomimetic, vasodilatory, anti- arrhytmic, analgesic, anti-bacterial, anti- hyperglycemic activities; traditional medicine, psychotropic a stimulant activities); Flavonoids (pharmacological activities (anti-allergic, anti-inflammatory, anti- oxidant, anti-microbial, anti-cancer, anti- diarrheal, against cardiovascular diseases) phenolic acids, anthraquinone, saponin) Duan et al., 2016 Tab. 4: Extracted value added compounds and their sources, composition of DESs used for extraction of these compounds, and biological activity of extracted compounds (Jablonsky et al., 2018, Jablonsky and Sima, 2019).
- 16. Substrate Solvents Extracted value added compounds and their biological activities or function Ref. Lonicerae japonicae ChCl/Bu-diol Phenolic compounds chlorogenic acid (reduction of blood pressure, possible anti-inflammatory effect), caffeic acid (anti-oxidant, anti-flammatory activity) Peng et al., 2016 Corncob ChCl/U; ChCl/Gly; ChCl/imidazole Monomeric sugars (food additives) Procentese et al., 2015 Equisetum palustre ChCl/Bet hydrochlorid/EG Flavonoids pharmacological activities (anti- allergic, anti-inflammatory, anti-oxidant, anti- microbial, anti-cancer, anti-diarrheal, against cardiovascular diseases) Qi et al., 2015 Grape skins ChCl/Glu; ChCl/Fru; ChCl/Xyl; ChCl/Gly; ChCl/MaA Polyphenols (dietary and cosmetic supplements, Ayurveda - traditional medicine) Radošević et al., 2016 Picea abies bark ChCl/LacA; ChCl/GlyA; ChCl/MalA; ChCl/TartA; ChCl/OxA; ChCl/CitA; ChCl/Gly; ChCl/Maleic acid; ChCl/MaA Polyphenols (dietary and cosmetic supplements, Ayurveda - traditional medicine) Škulcová et al., 2018c Salvia miltiorrhiza Bunge ChCl/Bu-diol Cryptotanshinone (anti-tumor), tanshinone (anti- cancer, antioxidant, anti-inflammatory, cytotoxic against a variety of cell lines) Wang et al., 2016 Cajanus cajan leaves ChCl/maltose; ChCl/Gly; ChCl/Bu-diol; ChCl/EG; ChCl/Glu; ChCl/Suc; ChCl/maltose; ChCl/sorbitol; ChCl/CitA; ChCl/MaA; ChCl/LacA; CitA/Glu; CitA/Suc; LacA/Glu; LacA/Suc Phenolic acids, therapeutic effect, plasmodiosis, diabetes, treatment of femoral head, anti-oxidant Wei et al., 2015b Tab. 4: Extracted value added compounds and their sources, composition of DESs used for extraction of these compounds, and biological activity of extracted compounds (Jablonsky et al., 2018, Jablonsky and Sima, 2019)
- 17. Algae industry • Content of proteins as high as 40-50 % on dry weight • Pigments from algae • Main products ▫ Algae oils ▫ Proteins/carbohydrates ▫ Biomass – fibres
- 18. DES composition Molar ratio Treated biomass Extracted compounds Ref. ChCl and Gly, EG, 1,3-propanediol; 1,4 - butanediol different Chlorella vulgaris Polyphenols Mahmood et al. 2019 ChCl/OxA, ChCl/EG, U-Acetamide Chlorella sp. Lipids Lu et al. 2016 ChCl/Gly or ChCl/EG Brown algae Fucoidan Jang et al., 2015 ChCl/formic acid (1:1 ; 1:2; 1:3); ChCl/AcH (1:1; 1:2; 1:3); ChCl/OxA (1:1); ChCl/propanedioic acid (1:1) (1:1 ; 1:2; 1:3); (1:1; 1:2; 1:3); (1:1); (1:1) Chlorella sp. and Chlorococcum sp. Fatty acid methyl esters Pan et al., 2017 Tab. 5 Application of green solvents on Algae (Jablonsky et al., 2018, Jablonsky and Sima, 2019)
- 19. Nature of oil industry • Virgin olive oil: extraction of phenolic compounds • Palm oil: extraction of tocopherols and tocotrienols, sugar production from waste • Edible oils: removal of lead and cadmium to improve oils quality • Safflower: source of oil and phenolic metabolites
- 20. DES composition Molar ratio Treated biomass Extracted compounds Ref. MaL/ChCl-water 2:4:2 oil palm biomass residues, empty fruit bunch lignin content in delignified biomass Yiin et al., 2017 MaL/monosodium glutamate/water 3:1:5 oil palm biomass residues, empty fruit bunch lignin content in delignified biomass Yiin et al., 2017 ChCl/EG, [NH3(Et)]Cl /Gly ChCl/U 1:2 Oil palm trunk fibres Pretreatment of fibres and enzymatic hydrolysis Zulkefli et al., 2017 [NH3(Et)]Cl/Gly 1:2 Oil palm trunk fibres Swelling and dissolution of fibres Abdulmalek et al., 2017 ChCl/U 1:2 Oil palm empty fruit bunch fibres Pretreatment of biomasss for sugar production Md Nor et al., 2016 ChCl/EG , ChCl/Gly, ChCl/xylitol, ChCl/formic acid 1:1 Palm bark Protocatechuic and caffeic acid, catechins, epicatechin Fu et al., 2017b ChCl/MalA Crude palm oil Tocols Abdul-Hadi et al., 2015 Tab. 6 Application of green solvents on waste from oil industries (Jablonsky et al., 2018, Jablonsky and Sima, 2019).
- 21. Pretreatment and fractionation of biomass by deep eutectic solvents Fig. 3: Delignification o wood by deep eutectic solvents (Jablonsky and Sima, 2019)
- 22. Pretreatment and fractionation of biomass by deep eutectic solvents (Tab. 7) (Jablonsky and Sima, 2019) Solvent Molar ratio Sample Conditions Effects Remarks Ref. ChCl/Gly/AlCl3·6H2O 1:2:(0.1; 0.13; 0.2; 0.28; 0.33) Poplar wood 1 g sample, 20 g DES, 110, 120, 130 °C for 4 h Efficiency of delignification (EfcK) 61.29%; 75.15%; 89.22%, 66.44%; 87.83%; 98.45% 79.07%; 93.40%; 105.00% 83.66%; 95.46%; 105.21% 83.57%; 95.11%; 105.26% Fractionation of biomass, lignin recovery and characterisation Xia et al., 2018 ChCl/OxA 1:1 Corncob 0.3 g corncob, 6 g DESs magnetically stirred at 90 °C for 24 h. 98.5% Pretreatment of biomass, and enhance the enzymatic hydrolysis and production of glucose Zhang et al., 2016b ChCl/LacA 1:2 Corncob 0.3 g corncob, 6 g DESs magnetically stirred at 70; 80; 90; 100; 110 °C for 24 h 18.1%; 31.1%; 42.7%; 65.8%; 95.5% Pretreatment of biomass, and enhance the enzymatic hydrolysis and production of glucose Zhang et al., 2016b ChCl/LacA 1:15 Corncob 0.3 g corncob, 6 g DESs magnetically stirred at 90 °C for 24 h. 93.1% Pretreatment of biomass, and enhance the enzymatic hydrolysis and production of glucose Zhang et al., 2016b ChCl/LacA 1:2 1:4 1:6 1:8 1:10 Salix matsudana cv. Zhuliu (Willow) 2.5 g samples, solid to solvent ratio 1:30, 90– 120 °C, and time 6–42 h molar ratio 1:10 at 120 °C, 12 h, efficiency of delignification 91.82% Delignification of biomass Li et al., 2017b
- 23. Solvent Molar ratio Sample Conditions Effects Remarks Ref. ChCl/OxA·2H2O 1:1 Poplar wood flour 0.5 g sample, 10 g DES heat in oil bath: 80 °C, 110 °C, 9 h 90.6% for 110°C Delignification of biomass, characterisation of lignin and cellulose properties Liu et al., 2017 ChCl/EG 1:2 Corncob 0.3 g corncob, 6 g DESs magnetically stirred at 90 °C for 24 h. 87.6% Pretreatment of biomass, and enhance the enzymatic hydrolysis and production of glucose Zhang et al., 2016b ChCl/LacA 1:10 Corncob 0.3 g corncob, 6 g DESs magnetically stirred at 90 °C for 24 h. 86.1% Pretreatment of biomass, and enhance the enzymatic hydrolysis and production of glucose Zhang et al., 2016b ChCl/OxA·2H2O 1:1 Poplar wood flour 0.5 g sample, 10 g DES heat in microwave; 800 W, 80 °C, heating-up 2 min., retention time 1,3 and 8 min 81.8% for 3 min, 78.2% for 8 min Delignification of biomass, characterisation of lignin and cellulose properties Liu et al., 2017 ChCl/LacA 1:2 Switchgrass –L, Corn stover –L, Miscanthus-L 2.5 g sample, 25 g DES, microwave irradiation 45 s, 800 W 72.23% 79.60% 77.47% Delignification of biomass, lignin recovery, pretreatment effect on enzymatic hydrolysis Chen & Wang, 2018 ChCl/LacA Poplar wood 0.6 g samples, 6 g DES, 90 °C, 6 h; 120 °C, 3 h; 145 °C, 69 h; 180 °C, 0.5 h 90°C, 25.2% 120°C, 72.1% 145°C, 78.5% Delignification of biomass, lignin recovery and characterisation Alvarez-Vasco et al., 2016 ChCl/LacA 1:5 Corncob 0.3 g corncob, 6 g DESs magnetically stirred at 90 °C for 24 h. 77.9% Pretreatment of biomass, and enhance the enzymatic hydrolysis Zhang et al., 2016b
- 24. Solvent Molar ratio Sample Conditions Effects Remarks Ref. ChCl/OxA·2H2O 1:1 Poplar wood flour 0.5 g sample, 10 g DES heat in oil bath: 80 °C, 110 °C, 9 h 90.6% for 110°C Delignification of biomass, characterisation of lignin and cellulose properties Liu et al., 2017 ChCl/EG 1:2 Corncob 0.3 g corncob, 6 g DESs magnetically stirred at 90 °C for 24 h. 87.6% Pretreatment of biomass, and enhance the enzymatic hydrolysis and production of glucose Zhang et al., 2016b ChCl/LacA 1:10 Corncob 0.3 g corncob, 6 g DESs magnetically stirred at 90 °C for 24 h. 86.1% Pretreatment of biomass, and enhance the enzymatic hydrolysis and production of glucose Zhang et al., 2016b ChCl/OxA·2H2O 1:1 Poplar wood flour 0.5 g sample, 10 g DES heat in microwave; 800 W, 80 °C, heating-up 2 min., retention time 1,3 and 8 min 81.8% for 3 min, 78.2% for 8 min Delignification of biomass, characterisation of lignin and cellulose properties Liu et al., 2017 ChCl/LacA 1:2 Switchgrass –L, Corn stover –L, Miscanthus-L 2.5 g sample, 25 g DES, microwave irradiation 45 s, 800 W 72.23% 79.60% 77.47% Delignification of biomass, lignin recovery, pretreatment effect on enzymatic hydrolysis Chen & Wang, 2018 ChCl/LacA Poplar wood 0.6 g samples, 6 g DES, 90 °C, 6 h; 120 °C, 3 h; 145 °C, 69 h; 180 °C, 0.5 h 90°C, 25.2% 120°C, 72.1% 145°C, 78.5% Delignification of biomass, lignin recovery and characterisation Alvarez-Vasco et al., 2016 ChCl/LacA 1:5 Corncob 0.3 g corncob, 6 g DESs magnetically stirred at 90 °C for 24 h. 77.9% Pretreatment of biomass, and enhance the enzymatic hydrolysis Zhang et al., 2016b Irrespective to kind of biomass and operation conditions, ..ChCl and LacA is the most effective in lignin removing
- 25. Kappa number Viscosity [mL g−1] Degree of polymerization Slc [%] Efc [%] Kraft pulp 1 *1 21.7 789 1157 - - ChCl/OxA 13.3 648 930 5.96 38.7 ChCl/MaA 13.2 772 1130 52.02 39.2 Alan/LacA 12.3 784 1149 206.48 43.3 ChCl/LacA 13.5 775 1134 58.27 37.8 Oxygen delignified pulp 1 11.8 569 805 4.48 45.6 Oxygen delignified pulp 1 11.8 569 805 - - ChCl/OxA 11.7 185 233 0.03 0.8 ChCl/MaA 10.4 406 554 0.86 11.9 Alan/LacA 10.4 532 747 3.79 11.9 ChCl/LacA 10.1 429 590 1.22 14.4 Kraft pulp 2 14.3 851 1258 - - ChCl/OxA 11.1 490 683 0.88 22.4 ChCl/MaA 12.3 780 1113 2.82 14.0 Alan/LacA 11.2 800 1160 6.01 21.7 ChCl/LacA 11.8 745 1085 2.34 17.5 Table 8: Characterization and effect on pulp properties after DES delignification (Majová et al., 2017) The selectivity of delignification (Slc,%) was expressed as a decrease in Kappa number on the unit change of the intrinsic viscosity. The efficiency of delignification (Efc) was expressed as a decrease in Kappa number on the unit change of the initial Kappa number of pulp (Majová et al. 2017).
- 26. Production of nanocellulose, nanofibers and modification of cellulose by deep eutectic solvents (Jablonsky et al., 2018, Jablonsky and Sima, 2019). 1. Cellulose nanocrystals; 2. Cellulose nanofibrils; 3. Modification of cellulose
- 27. Solvent Molar Ratio Sample Conditions Effects Ref. U/LiCl 5:1 Softwood pulp 1.5 g pulp, 150 g DES, succinic anhydride (9.27 g), temperature 70, 80, 90, 100 and 110°C, stirred 2, 6 or 24 hours The optimal conditions: 2 hours, 70-80°C, product transparent viscose nanogel (Selkala et al., 2016) ChCl/U 1:1.75 Recycled boxboard, milk container- board, fluting board, bleached birch kraft pulp 25 g od pulp, 30% moisture content, mixed 2 hour with 2843 g DES, washed samples was fibrillated in Masuko supermass colloider grinder Solid content of the hydrogels were between 1.5 to 2%. (Laitinen et al., 2018) ChCl/U 1:1.75 Recycled boxboard, milk containerboard, fluting board, bleached birch kraft pulp 25 g od pulp, 30% moisture content, mixed 2 hour with 2843 g DES, washed samples was fibrillated in Masuko supermass collider grinder Absorption capacity 142.9 g.g-1 for bleached birch kraft pulp (Laitinen, O. et al., 2017) ChCl/OxA 1:1 1:2 1:3 Bleached cotton cellulose 1 g cellulose, 100 ml DES, 1 hour, 80 or 100°C, ultrasonic homogenisation 300 W, 20 kHz, and centrifugation of suspension Esterification of hydroxyl groups, the better dispersion of cellulose nanocrystals (Ling et al., 2018) Aminoguanidine·HCl/Gly 1:2 Bleached kraft birch pulp 10 g dialdehyde cellulose, 200 g DES, time 5 to 60 min, 55 and 75°C (Li et al., 2018) ChCl/OxA·2H2O , ChCl/p-toluenesulfonic acid monohydrate, ChCl/LevA 1:2, 1:1 1:1 1:2, Softwood pulp 1.2 g pulp, 120 g DES, 2-4 h, 60-120°C, fibrillation by microfluidizer (Sirvio et al., 2016) Ammonium thiocyanate/U 1:2 Bleached birch kraft pulp 4 g pulp, 400 g DES, 2 h, 100°C, fibrillation by microfluidizer Cellulose nanofibrils (with 13.1 – 19.3 nm), tensile strength up to 189 MPa (Li et al., 2017) Guanidine hydrochloride/U 1:2 Bleached birch kraft pulp 4 g pulp, 400 g DES, 2 h, 100°C, fibrillation by microfluidizer Cellulose nanofibrils (with 13.0 – 15.8 nm), tensile strength 135-163 MPa (Li et al., 2017)
- 28. Animal products-based food processing industries • proteins, lipids and ashes 1. Extraction of animal-based biomass aimed at isolating value-added compounds or substances present in the biomass; 2. Employment of DESs as a medium for storage, investigation of properties and stability of biologically active compounds isolated from animal-based biomass; 3. Extraction of value-added compounds, mainly proteins at laboratory level aimed at verifying the extraction efficiency of pure DESs or their mixture with water, as well as protein partitioning.
- 29. Substrate Solvents Extracted value added compounds and their biological activities or function Ref. Bovine serum albumin; trypsin; ovalbumin; calf blood Bet/U/water; Bet/MeU/water; Bet/Glu/water; Bet/sorbitol/water; Bet/Gly/water; Bet/EG/water Proteins food additives Li et al., 2016 Wool ChCl/U Keratin wound healing, tissue engineering, drug applications, biomaterials science Moore et al., 2016 Cod skins ChCl/U; ChCl/EG; ChCl/Gly; ChCl/LacA; ChCl/AcA; ChCl/OxA Collagen peptides; reparative ability to skin, anti-hypertensive, anti- oxidant Bai et al., 2017 Bovine serum , albumin, ovalbumin and trypsin ChCl/U; [N(Me)4]Cl/U; [N(Pr)4]Br/U; ChCl/(MeU) bovine serum , albumin, ovalbumin and trypsin Zeng et al. 2014 Rabbit hair ChCl/OxA keratin Wang et al., 2018 Wool fiber ChCl/U wool keratin Jiang et al. 2018 Tab. 10 Application of green solvents on animal products and waste (Jablonsky et al., 2018, Jablonsky and Sima, 2019)
- 30. Brewing industry • by-products are originate from raw materials used to make beer, barley, hops and yeast • sludge of brewing industry. • Phenolic compounds such as gallic acid, gallocatechin, protocatechuic acid, epigallocatechin, catechin, 4-hydroxybenzoic acid, caffeic acid, epicatechin, p-coumaric acid, isoquercetin, ferulic acid, acetosyringone, resveratrol, quercetin, apigenin, kaempferol, naringenin
- 31. Dairy industry • huge profitable constituents, for example, β- lactoglobulin, α-lactalbumin, immunoglobulin, lactoferrin, and lactoperoxidase
- 32. Future trends and concluding remarks The excellent properties of DESs, NADESs and LTTMs, such as sustainability, biodegradability, pharmaceutical acceptable toxicity and high extractability of compounds with diverse polarity, highlight their potential as green solvents Questions or opportunities of other research activities (Jablonsky and Sima 2019): • Capacity of ChCl-containing DESs or NADESs to react with a substrate or extractable substances leading to adsorbable organic halides. This issue is of extreme importance given the necessity to restrict the use of such halides and even to reject them based on the mentioned 12 principles of green chemistry from the area of green technologies. • Frequently, the impact of water for extraction of substances showing pharmacokinetic properties has been investigated. Such an impact depends, however, in a considerable extent, also on the type, nature and properties of purposefully extracted substance. • Determination and arise of available extraction methods (e.g., MAE, UAE, SFE) and choice of the optimal conditions (solid to liquid ratio, particle size, content of water, time, temperature), and parameters of selected method of extraction (irradiation or ultrasonic power, type of co-solvent) for extraction of selected target compounds by green solvents is the key parameter for spreading this area.
- 33. Future trends and concluding remarks • As indicated above, following the pharmacokinetic properties should play a non- negligible role. There are papers describing the recovery of model pure compounds, however, in selection of extracted substances, less attention is devoted to their suitability for using in pharmaceutical industry. • In spite of the fact that several characteristics of extraction systems consisting of DESs, NADESs and LTTMs are frequently described (viscosity, polarity, density), more detailed investigation of two- or more-component extraction systems or predictability of their properties is still in the infancy stage. • Computed properties (Absorption, Distribution, Metabolism, Excretion and Toxicity – ADMET; example) associated with extracted substances are key parameters for further progress and spreading of breakthrough technology for extraction of biologically active substances.
- 34. THANK YOU This work was supported by the Slovak Research and Development Agency under the contracts No. APVV-15-0052, APVV-14-0393 and APVV-16-0088 and VEGA grant 1/403/19.
- 35. List of abbreviations AcA Acetic acid Alan Alanine Bet Betaine Bu Butyl Bu-diol 1,4-Butanediol Bu-OH 1-Butanol Bz Benzyl CF3CONH2 2,2,2-Trifluoroacetamide CitA Citric acid EG Ethylene glycol Et Ethyl Fru Fructose Glu Glucose Gly Glycerol GlycA Glycolic acid ChCl Choline chloride Ch-glut Choline glutarate LacA Lactic acid LevA Levulinic acid MaA Malic acid MalA Malonic acid Me Methyl OxA Oxalic acid Ph Phenyl Pr-diol 1,3-propanediol Pr-OH 1-Propanol Prol Proline Sor Sorbose Suc Sucrose TartA Tartaric acid U Urea Xyl Xylose [N(Bu)4]Br Tetrabutylammonium bromide [N(Et)4]Cl Tetraethylammonium chloride [N(Me)(Oc)3]Cl N-methyl-N,N,N-tri-n-octylammonium chloride [N(Me)4]Cl Tetramethylammonium chloride [N(Pr)4]Br Tetrapropylammonium bromide [NH3(Et)]Cl Ethylammonium chloride [P(Allyl)(Ph)3]Br allyltriphenylphosphonium bromide [P(Me)(Ph)3]Br Methyltriphenylphosphonium bromide
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Editor's Notes
- The great scientist Mendeleev within his investigation of the composition of petroleum recognized its importance and value as feedstock for petrochemicals. He is credited with a remark that burning petroleum as fuel "would be akin to firing up a kitchen stove with bank notes" The same attitude can be applied towards biomass containing numerous valuable chemical compounds.
- Every year 200 bilions tonnes of biomass is produced through photosynthesis. Approximately 75% of all biomass is composed of saccharides, 20% is made of biopolymer named lignin, and the remainder (5%) consists of extractives The development of fractionation methods is varied according to feedstock and final products. One of the promising technologies is the use of ionic liquids, mainly of DESs and NADESs
- Stemming from the logical general tendency to apply predominantly environmentally friendly chemicals, the attention of scientists, researchers and industrial technologists is focused on extraction techniques using green solvents as extractants. It is imperative to satisfy the requirements of 12 principles of green chemistry Deep eutectic solvents (DESs) are mixtures of two or more components - hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) - which can bond with each other to form a eutectic mixture having a final melting point that is lower than the melting point of the raw materials (HBD) and (HBA) becoming thus liquids at room temperature. When the compounds that constitute the DES are exclusively primary metabolites, namely, amino acids, organic acids, sugars, or choline derivatives, the DESs are called natural deep eutectic solvents (NADESs). The term low-transition temperature mixtures (LTTMs) is used for both eutectic mixtures (DESs and NADESs) as well as for liquids composed of natural high-melting-point starting materials which are not eutectic. Low-melting mixtures (LMMs) are green solvents based on bulk carbohydrates, sugar alcohols or citric acid combined with different ureas and inorganic salts. In both DESs and LMMs, the eutectic solvent is formed as a result of hydrogen-bond-promoted self-association interactions between their individual components
- Density is one of the key physical properties of DESs. As for the dependence of the DES density on the molar ratio of its constituents, the higher the HBA : HBD ratio, the higher the structural arrangement and the lower free volume of the DES. The higher the temperature, the greater mobility of the molecules. The molar volume thus increases and consequently density decreases.
- Viscosity of most DESs is relatively high, when compared to water or traditional organic solvents in a wide range of temperatures. Viscosity of DESs can be modified by a change in HBA and HBD ratio, a temperature change, addition of water (or an organic solvent) or by addition of a salt.The important factor of the high viscosity of DESs are hydrogen bonds between their components
- Value of pH may significantly influence the course of chemical reactions. It is, thus, an important factor also for application of DESs in catalytic, biochemical and electrochemical processes Biomass processing and effective extraction of value-added compounds is influenced by the nature of the biomass and properties of the extractant used, including its pH. These effects will be illustrated for treating of plant biomass. When using hydrochloric acid or sulphuric acid (pH < 7), a fraction of hemicelluloses dissolves. Strongly acidic solution (pH < 2) has no substantial impact on hemicelluloses’ dissolution. Solubility of lignin is influenced by pH as well.
- Thermal stability is the key factor which should be taken into account when deciding on DESs large-scale application. High temperature can cause changes in the mass of DES due to its evaporation or decomposition. From the viewpoint of DES introduction into practice, its resistance to changes at long-term constant temperature – called long-term isothermal stability – must be known. This DES is thus not suitable for the use at temperature exceeding 80 °C. Weight loss for all investigated DESs depends on temperature and the loss is an exponential function of temperature. Tolerable weight loss for the DESs happens at 80 °C.
- Fields of application of deep eutectic solvents Application in electrochemistry, analytical chemistry, environmentally and material processing, and synthesis DESs and NADESs have been applied in extraction of value-added components from various natural raw materials (lignocellulosic biomass, bark, wood, algae can serve as examples) and wastes (e.g., those from vegetable oils, diary and beverage production and consumption)
- In case studies published mainly in the last three years, numerous value-added substances were obtained using various extraction techniques and green solvents. The attention was focused predominantly on biomass and biowaste containing a relevant amount of the substances, denoted usually as bioactive compounds. Taking the potential of renewable green biomass processing into account, the investigation of extraction was directed to isolate such substances in the highest possible yield and purity. The value-added substances isolated from any kind of biomass can be classified based on their biological properties, structural or chemical class, actual or potential applicability, etc. All these factors make unambiguous classification of extracted value-added compounds impossible. The spectrum of the properties of these compounds is really wide (anticoagulative, anti-inflammatory, antioxidant, hepatoprotective, antihypertensive, antitumor, antimicrobial, anticancer, antidiarrheal, antiallergic, antiatherosclerotic, estrogenic, insecticidal, antimutagenic, pharmacokinetic, antiprileferative, neuroprotective, antiangiogenetic, antagonist and other) and, therefore, their application is possible in different domains. The most important use of isolated bioactive compounds includes pharmaceutical and biomedical applications, and last but not least application in food industry playing the role of additives and functional substances, nutraceuticals introduced in industrial food industry to enhance food quality or gastronomy.
- Tab. 3: Illustrative list of value-added bioactive compounds extracted by metal-free Type III DESs and sources of the compounds
- Tab. 5: Extracted value added compounds and their sources, composition of DESs used for extraction of these compounds, and biological activity of extracted compounds
- Very interesting group of feedstock biomass are algae. The reason is that algae are typically very rich in proteins with content as high as 40-50 % on dry weight basis depending on the strain used, and contains pigmentation metabolism of algae which exhibits beneficial biological compounds with anti-inflammatory, antiobesity, antioxidant, antiangiogenic and neuroprotective activities Main products: Algae oils; Proteins/carbohydrates; and Biomass – fibres
- Mahmood, Lu, Jang and Pan et al. realised the extraction by DESs with the different algae (chlorella or brown algae). Extracted compouns were polyphenols, lipids, fucoidan or fatty acids.
- Of the vegetable oils, the attention has been focused predominantly on olive, palm, and safflower oils. These oils are used mainly for eating and preparing foodstuff products. Total world annual production of olive oils approaches 3 million tonnes. Thanks to the content of fatty acids and phenolic compounds, olive oil exhibits numerous health benefits suppressing coronary heart diseases, neurodegenerative diseases and atherosclerosis. Phenolic group of virgin olive oil is a complex fraction composed by at least 36 structurally different phenolic compounds (Cicerale et al., 2010). In this fraction, four main types of phenolic compounds are linked to positive bioactive properties: phenolic acids and phenolic alcohols, secoiridoid derivatives (aglycone and ligstroside), lignans (pino and acetoxypinoresinol) and flavones (luteolin and apigein).
- Tab. 6 Application of green solvents on waste from oil industries
- Conversion and utilization of lignocellulose biomass have been extensively studied in the past decades. The main target is an effective pretreatment which can be achieved via the cleavage of lignin structure. The pretreatment of feedstocks is important for the effective hydrolysis of reducing sugars to occur before subsequent fermentation into value-added products Sugar recovery is 20% for biomass feedstock without pretreatment, however applying this process the recovery can reach 80%. Separation of individual components is complicated also by their mutual interactions through various lignin-saccharide bonds. Similarly to other solvents used to dissolve lignin in lignocellulosic matrix, the use of DESs is conditioned by their ability to penetrate into the biomass structure and to contact the dissolved component. Due to a DES higher viscosity, to fulfil this requirement is not a simple task. The first step is transfer through lumen to the third secondary wall (S3 in Fig. 15). This wall contains lower content of lignin and DES start to dissolve/hydrolyse polysaccharides, particularly hemicelluloses. Only then DES penetrates through other structures and begins to remove lignin. A simplified progress of delignification is depicted in Fig. 16.
- Table lists conditions of treatment of individual of biomass kinds and their effects. In addition, supplementary data and remarks are given as well in the column Remarks. Individual research teams express the impact of DESs through different quantities. We have unified expression of the impacts through the efficiency of delignification (EfcK) expressed as a decrease in the content of lignin (or Kappa number) on the unit change of the initial content of lignin (or Kappa number). Based on the published results on the efficiency of lignin removal from various kinds of biomass, the most efficient DESs have been selected and included into Table 31. The highest is achieved by the ternary ChCl/Gly/AlCl3.6H2O DES (Xia et al., 2018); 98.5% removal efficiency was determined using ChCl/OxA (1:1); 98.5% by ChCl/LacA (1:2); 93.1% by ChCl/LacA (1.15) (Zhang et al., 2016b); 91.82% by ChCl/LacA (Li et al., 2017b); 90.6% by ChCl/LacA (1:1) (Liu et al., 2017). Thus, irrespective to the kind of biomass and operation conditions, ChCl/LacA is the most effective in lignin removing.
- A recent work (Majová et al., 2017) on delignification of pulps with different initial Kappa numbers: 21.7, 11.8, and 14.3 in the presence of three ChCl-based DESs systems (ChCl/LacA (1:9), ChCl/OxA (1:1), ChCl/MaA (1:1), and Alan/LacA (1:9) suggested that pulp with a higher initial Kappa number or lignin content possessed a greater fraction of easily removed lignin fragments. Delignification efficiency of lignin removal, selectivity and impact on the degradation of cellulose are shown in Table 32.
- Nanocellulose is cellulose consisting of particles possessing at least one dimension less than 100 nanometers. In general, this term covers different types of cellulosic materials such as nanocrystalline cellulose (NCC), cellulose nanocrystals (CNC), nanofibrillated cellulose (NFC), cellulose nanofibrils (CNF), microfibrillated cellulose (MFC), carboxymethylated cellulose (CMC), microcrystalline cellulose (MCC), cellulose filaments (CF), and cellulose whiskers (Shak et al., 2018). Nanocellulose is derived from different type of lignocellulosic sources such as wood, cellulose fibres from cotton, hemp, wheat straw, sisal, hemp, bleached pulps, the main source is woodpulp. It can be prepared by two principal ways. One of them is a chemical process, acid hydrolysis, giving rise to highly crystalline and rigid nanoparticles which are shorter (100 – 1000 nanometers). The other lies in mechanical procedures comprising homogenization, microfluiodization or grinding . The primary focus is application and spreading used nano-fibrillated products for fibre-rich products containing nanocellulose, nanofibers, nanocrystals or nanocomposites. The application of DESs to modified cellulose creates the new roadmap to sustainable cellulose upgrading. Other potential applications for nanocellulose or functionalized polymer matrices lie in surface sizing and coating processing as a barrier against vapour or gases, introducing lysols, suspensions, emulsions and foams, hydrogels and food thickeners into food packaging
- Large volumes of protein-rich residual raw materials, such as heads, bones, carcasses, blood, skin, viscera, hooves and feathers, are created as a result of processing of animals from fisheries, aquaculture, livestock and poultry sectors (Aspevik et al., 2017). Animal co-products are composed of three principal ingredients: proteins, lipids and ashes in varying quantities
- Beer production is an extensively studied biotechnological process that generates various by-products. The most common by-products are originate from raw materials used to make beer, barley, hops and yeast. The sludge of brewing contains the phenolic compounds such as gallic acid, gallocatechin, catechin, epicatechin, p-coumaric acid, isoquercetin, ferulic acid, resveratrol, quercetin.These bioactive compounds may be a good source of compounds with several applications in the food industry, as food ingredients and nutraceuticals, in the cosmetics, and in pharmaceutical industries. Similarly as in the dairy industry as well in this area have not yet been shown the benefits of using new green solvents for the isolation of biologically active substances, but the potential benefit is there for their application.
- A great potential lies also in the dairy industry, where the interest for recovery profitable constituents may be renewed and reinforced. The dairy processing industry contains huge profitable constituents, for example, β-lactoglobulin, α-lactalbumin, immunoglobulin, lactoferrin, and lactoperoxidase. They are widely accepted as food ingredients (e.g., confectionery, bakery, health, and sport supplements), and have a high content of essential amino acids which may be used such as gelation, foaming, and emulsifying agents, which have different biological properties (antimicrobial, anticarcinogenic, and immunomodulatory activities). Advances in processing technologies and used new green solvents and it can bring them better use encourage applications in rich protein source with high biological value. Up to now the attention of researchers dealing with DES and NADES application has not been focused on the isolation of substances with added value from diary industry. In spite of that and mainly due to the potential of the industry, a breakthrough also in this field can be expected. It relates predominantly to the extraction of substances with a higher efficiency and purity, enhancing in some cases biological activity (e.g., antioxidant properties) of isolated substances. To be able to develop new drugs from these compounds, they should not only possess specific biological activity, but also have to display drug-like properties and favourable pharmacokinetic profiles.
- The excellent properties of DESs, NADESs and LTTMs, such as sustainability, biodegradability, pharmaceutical acceptable toxicity and high extractability of compounds with diverse polarity, highlight their potential as green solvents. It may be expected that a major focus of current green technology applications will be put, in the future, on the development of food ingredients and delivery systems for nutrients and supplements. A variety of extraction by DES and NADES can be applied to recover the target compounds and products from different type of biomass, food and agro-forest waste. Already at the end of the last century the trend oriented to obtaining phytochemicals from renewable natural sources or waste from their processing has evolved. This trend continues and progresses in scientific area in this century as well. Evolution of new extraction methods, mainly of extraction systems shifts the human knowledge a step further. Although ionic liquids have been known for some decades, it is just the field of development of new generation of eutectic mixtures and their application in the area of renewable sources and wastes has stimulated unpredictable possibilities of their exploitation. As far as the application of DESs, NADESs and LTTMs is concerned, the starting year is 2003. One of the consequences of the development is that currently nearly all universities have a scientific group dealing with such solvents and their application.