Exploring carbohydrate extraction from biomass using deep eutectic solvents: Factors and mechanisms

Deep Eutectic Systems: A Game Changer for Marine Bioactives Recovery

The extraction of bioactive compounds from marine natural products has gained increasing attention due to their diverse applications, such as in pharmaceuticals, nutraceuticals, and cosmetics. Yet, low extraction yields and toxicity associated with common solvents are a major bottleneck. Deep eutectic solvents (DESs) and natural deep eutectic solvents (NADESs) have emerged as promising green alternatives to conventional organic solvents, offering advantages such as biodegradability, greater environmental and economic sustainability, low toxicity, and enhanced extraction selectivity. This review provides a comprehensive analysis of the principles, physicochemical properties, and applications of DESs/NADESs to obtain bioactive compounds from marine organisms. Among the most recent works, it is possible to verify the success of NADESs to extract carrageenan from the seaweed Kappaphycus alvarezii; pigments from Palmaria palmata; and polyphenols and proteins from different brown seaweeds. NADESs have also shown high potential to extract other valuable compounds from marine by-products, such as chitin from crabs and shrimp shells, and also lipids and proteins from different fish species and protein rich extracts from tilapia viscera. The challenges for DESs/NADESs use at industrial scale are also discussed, and success cases are revealed, highlighting their potential as game changers for extracting bioactive compounds from marine organisms and driving the development of innovative biotechnological products.

Exploration of biomass fractionation and lignin removal for enhancing enzymatic digestion of wheat-stalk through deep eutectic solvent Cetyl trimethyl ammonium chloride:Lactic acid treatment

The cationic surfactant-based deep eutectic solvents (DESs) have attracted extensive attention due to their effectual destruction of the natural anti-degradation barrier structure in lignocellulose. In this research, functional DES Cetyl trimethyl ammonium chloride:Lactic acid (CTAC:LA molar ratio 1:0.5 to 1:6) was fabricated for pretreating wheat-stalk. The relationships of accessibility, lignin removal, xylan separation, and enzymolysis efficiency were explored. The highest delignification (88.3 %) and xylan removal (89.0 %) were obtained through the treatment with CTAC:LA (1:4, mol/mol, 160 °C, 60 min), acquiring 86.8 % of enzymolysis efficiency. The structure of CTAC:LA-treated wheat-stalk was changed to porous state, while the accessibility and crystallinity were substantially improved to 668.2 mg/g and 57.6 %, respectively. The lignin surface area declined from 672.7 to 335.4 m2/g. Furthermore, the structure of lignin disrupted by CTAC:LA was analyzed by 2D-HSQC NMR, implying that CTAC:LA could cleave the CO covalent bond and CC bond and degrade the S- and H-units in wheat-stalk lignin through interaction. The potential pretreatment mechanism was proposed through comprehensive exploration at the molecular level and macro level, and this built pretreatment process held great promise for valorizing biomass into highly valuable chemicals.

Glucomannan isolation from porang (Amorphophallus muelleri Blume) flour using natural deep eutectic solvents and ethanol: A comparative study

Ethanol is a common solvent to isolate glucomannan from porang (Amorphophallus muelleri Blume) flour (NPF). This study investigated the use of natural deep eutectic solvents (NADESs) in glucomannan isolation from NPF. NADESs formed by the hydrogen bond acceptors (choline chloride and betaine) and the hydrogen bond donors (glycerol, 1,2-propanediol, formic acid, and acetic acid) in varying molar ratios of 1:2, 1:3, and 1:4 were characterized to optimize glucomannan isolation. The results showed that higher molar ratios of NADES tended to yield porang glucomannan flour (PGF) with higher glucomannan content and viscosity. The gel of PGF exhibited pseudoplastic behavior. The FTIR spectra indicated that betaine-based NADES removed the acetyl groups from glucomannan chains. The PGF obtained from NADESs with a molar ratio of 1:4 was comparable to those obtained from ethanol with a glucomannan content of 87.34 %-93.28 % and a weight-average molecular weight of 9.12 × 105-1.20 × 106 g/mol.

Activities of proteases in deep eutectic solvents and removal of protein from chitin by subtilisin A in betaine/glycerol

This research intended to remove residual protein from chitin with proteases in deep eutectic solvents (DESs). The activities of some proteases in several DESs, including choline chloride/p-toluenesulfonic acid, betaine/glycerol (Bet/G), choline chloride/malic acid, choline chloride/lactic acid, and choline chloride/urea, which are capable of dissolving chitin, were tested, and only in Bet/G some proteases were found to be active, with subtilisin A, ficin, and bromelain showing higher activity than other proteases. However, the latter two proteases caused degradation of chitin molecules. Further investigation revealed that subtilisin A in Bet/G did not exhibit "pH memory", which is a universal characteristic displayed by enzymes dispersed in organic phases, and the catalytic characteristics of subtilisin A in Bet/G differed significantly from those in aqueous phase. The conditions for protein removal from chitin by subtilisin A in Bet/G were determined: Chitin dissolved in Bet/G with 0.5 % subtilisin A (442.0 U/mg, based on the mass of chitin) was hydrolyzed at 45 °C for 30 min. The residual protein content in chitin decreased from 5.75 % ± 0.10 % to 1.01 % ± 0.12 %, improving protein removal by 57.20 % compared with protein removal obtained by Bet/G alone. The crystallinity and deacetylation degrees of chitin remained unchanged after the treatment.

Algal carbohydrate polymers: Catalytic innovations for sustainable development

Algal polysaccharides, harnessed for their catalytic potential, embody a compelling narrative in sustainable chemistry. This review explores the complex domains of algal carbohydrate-based catalysis, revealing its diverse trajectory. Starting with algal polysaccharide synthesis and characterization methods as catalysts, the investigation includes sophisticated techniques like NMR spectroscopy that provide deep insights into the structural variety of these materials. Algal polysaccharides undergo various preparation and modification techniques to enhance their catalytic activity such as immobilization. Homogeneous catalysis, revealing its significance in practical applications like crafting organic compounds and facilitating chemical transformations. Recent studies showcase how algal-derived catalysts prove to be remarkably versatile, showcasing their ability to customise reactions for specific substances. Heterogeneous catalysis, it highlights the significance of immobilization techniques, playing a central role in ensuring stability and the ability to reuse catalysts. The practical applications of heterogeneous algal catalysts in converting biomass and breaking down contaminants, supported by real-life case studies, emphasize their effectiveness. In sustainable chemistry, algal polysaccharides emerge as compelling catalysts, offering a unique intersection of eco-friendliness, structural diversity, and versatile catalytic properties. Tackling challenges such as dealing with complex structural variations, ensuring the stability of the catalyst, and addressing economic considerations calls for out-of-the-box and inventive solutions. Embracing the circular economy mindset not only assures sustainable catalyst design but also promotes efficient recycling practices. The use of algal carbohydrates in catalysis stands out as a source of optimism, paving the way for a future where chemistry aligns seamlessly with nature, guiding us toward a sustainable, eco-friendly, and thriving tomorrow. This review encapsulates-structural insights, catalytic applications, challenges, and future perspectives-invoking a call for collective commitment to catalyze a sustainable scientific revolution.