Use of Deep Eutectic Solvents in the Treatment of Agro-Industrial Lignocellulosic Wastes for Bioactive Compounds

Lignocellulose is the most abundant component in nature since it refers to plant material. Beyond the enormous utilization of lignocellulose by human being, unignorable amount of waste is also formed simultaneously. Agro-industrial lignocellulosic wastes can cause environmental pollutions if not processed before discharged. An innovative approach for lowering the detrimental influences of lignocellulosic wastes is to consider them as a source of useful products rather than a waste to be decontaminated. Beyond the conventional techniques for evaluation of the wastes, new emerging techniques and the use of new solvents have drawn attention recently. Among new generation solvents, deep eutectic solvents (DESs) have been increasingly used in the treatment of lignocellulosics to produce value-added products such as biofuels, chemicals, and solvents and also used for the recovery of bioactive phenolic compounds. DESs are used extensively for fractionation of lignocellulosic wastes, often in combination with enzymatic hydrolysis of the biomass. On the other hand, extraction and recovery of bioactive compounds are also under research using DESs. This mini review summarizes the very recent literature reports on the use of DESs in treating agro-industrial wastes within the concept of valorization of biomass

Screening of Natural Deep Eutectic Solvents for the Recovery of Valuable Phenolics From Waste of Shalgam Juice Process

Shalgam juice is one of the most popular non-alcoholic beverages in Türkiye and also in many countries. The high amount of production, regarding the high amount of consumption leads to an inevitable amount of solid waste.  This amount reaches to almost 12 million kg of fermented black carrot annually. The accumulation of this waste causes fatal environmental pollution. The waste of shalgam juice process, fermented black carrot, retains significant amount of valuable components, such as phenolics, flavonoids, and anthocyanins. In this study new generation green solvents, Natural Deep Eutectic Solvents (NADESs) were screened for the extraction of valuable phenolics from fermented black carrot using ultrasound assisted extraction. The NADESs used were selected from four different groups such as acidic, sugar-based, choline chloride-sugar based and polyol-based. According to the results, the members of polyol and choline chloride sugar NADESs showed up. Choline chloride-glycerol (polyol group), extracted the highest total phenol amount (16.04 mg/g) and also provided the highest antioxidant activity (81.77%). On the other hand, NADESs belonging to choline chloride-sugar group were effective for the extraction of flavonoids and monomeric anthocyanins. Namely, choline chloride-fructose-water extract contained 21.45 mg/g of total flavonoids, while choline chloride-sucrose-water extract contained 1680.51 mg/kg of total monomeric anthocyanins. The performances of NADESs tested were found to be higher than that of water and ethanol showing the high yield recovery of valuable phenolics with NADESs. The results exhibited the significance of the components inside the waste. The remaining valuable content could be easily and efficiently extracted using NADESs and these extracts –as a mixture or after purification- can furtherly be used for different purposes in different fields, such as cosmetics, antioxidant preparations, etc, using a zero-cost waste as the input of the processes

Use of deep eutectic solvents as catalyst: A mini-review

Deep eutectic solvents (DESs) exhibit numerous advantages over conventional ones used in several chemical and biochemical processes. Besides addressing most of the principles of green chemistry, DESs can also act as catalyst depending on their nature. The use of DESs as acid catalyst has several advantages such as utilization at stoichiometric amount, non-toxicity, possibility of the recovery, similar or higher catalytic effect than the acid itself alone, the recyclability and reusability without a significant loss of activity. In this mini-review, the state- of-the-art in the use of DESs as catalyst is presented. The DESs, which show Lewis type acidity, Brønsted type acidity and other types of catalytic influence in various types of reactions including esterification, organic synthesis, glycolysis and depolymerisation are presented and their roles in the reactions are discussed

Investigation of a green process for the polymerization of catechin

<p>Flavonoids are polyphenolic secondary plant metabolites which possess antioxidant and anti-inflammatory properties. Besides, they have been shown to exhibit increased antioxidant properties in their polymerized form. Catechins are one of the attractive class of flavonoids which belong to the group of flavan-3-ols. Polymerization of catechins have been investigated in numerous studies indicating the requirement of certain amount of organic solvent to provide the solubility of the monomer. However, many research projects have been conducted recently to replace toxic organic contaminants of the processes with environmentally friendly solvents. In this aspect, deep eutectic solvents (DESs) that are regarded as “green solvents” have been studied extensively in various enzyme catalyzed reactions. In the present study, we focused on establishing a green pathway for laccase catalyzed polycatechin synthesis by replacing organic solvent content with DESs as green solvents. For this aim, various parameters were investigated, such as DES types and concentrations laccase amount and reaction time. Consequently, the highest molecular weight polycatechin was obtained using 5% (v/v) B–M, 125 U laccase in 1 hr of reaction time, at 30°C, as 4,354 ± 678 g mol⁻¹. Corresponding X/XO inhibitory activity and superoxide radical scavenging activities were achieved as, 59 and 50%, respectively.</p

The effect of natural deep eutectic solvents on laccase activity and oligomerization of rutin

Natural deep eutectic solvents (NADESs) were investigated for the activity and stability of the laccase enzyme. Laccase was found to be active only in a low amount of choline chloride containing NADESs while it maintained its activity both in high and low amounts of betaine containing NADESs. Rutin, as a flavonoid monomer shows high antioxidant, antibacterial, antiviral and anti-inflammatory properties and these properties are enhanced in the polymerised form. In this study, the organic co-solvent that is conventionally used in the oligomerization of rutin was replaced with two different green solvents, choline chloride-ethylene glycol (1:2 molar ratio) and betaine-mannose (5:2 molar ratio). LC-MS results revealed spontaneous derivatization of rutin as well as the oligomerization of the derivatives besides rutin. The final products were found to have enhanced superoxide radical activity. In this study, enzymatic oligomerization of rutin was investigated for the first time in the presence of eco-friendly green solvents presenting an alternative pathway without any toxic components.</p