Separation of water-soluble lignins from lignocellulosic biomass provides a new and still poorly exploited feedstock to increase the sustainability of biorefineries. We applied derivatization followed by a reductive cleavage (DFRC) method, 2D-HSQC-NMR, and ³¹PNMR after ³¹P-labeling, to investigate molecular composition in water-soluble lignins obtained by alkaline oxidation from three biomass materials for energy (miscanthus, giant reed and an industrially pre-treated giant reed). Chromatographic identification of lignin products cleaved by DFRC showed a large predominance of guaiacyl (G) units in all biomasses and a lesser abundance of syringyl (S) and p-coumaryl (P) monomers. Our S/G ratios disagree with those reported in literature by other lignin separation methods. Carboxyl functions (ferulic and pcoumaric acids) were revealed by heterocorrelated ¹H–¹³C HSQC-NMR, and confirmed by ³¹P-NMR spectra of ³¹ P-labeled lignin molecules. An understanding of molecular composition of water-soluble lignins from biomass sources for energy is essential for lignin most efficient exploitation in either industrial or agricultural applications.

Natural biopolymers have become key players in the preparation of biodegradable food packaging. However, biopolymers are typically highly hydrophilic, which imposes limitations in terms of barrier properties that are associated with water interactions. Here, we enhance the barrier properties of biobased packaging using multilayer designs, in which each layer displays a complementary barrier function. Oxygen, water vapor, and UV barriers were achieved using a stepwise assembly of cellulose nanofibers, biobased wax, and lignin particles supported by chitin nanofibers. We first engineered several designs containing CNFs and carnauba wax. Among them, we obtained low water vapor permeabilities in an assembly containing three layers, i.e., CNF/wax/CNF, in which wax was present as a continuous layer. We then incorporated a layer of lignin nanoparticles nucleated on chitin nanofibrils (LPChNF) to introduce a complete barrier against UV light, while maintaining film translucency. Our multilayer design which comprised CNF/wax/LPChNF enabled high oxygen (OTR of 3 ± 1 cm³/m²·day) and water vapor (WVTR of 6 ± 1 g/m²·day) barriers at 50% relative humidity. It was also effective against oil penetration. Oxygen permeability was controlled by the presence of tight networks of cellulose and chitin nanofibers, while water vapor diffusion through the assembly was regulated by the continuous wax layer. Lastly, we showcased our fully renewable packaging material for preservation of the texture of a commercial cracker (dry food). Our material showed functionality similar to that of the original packaging, which was composed of synthetic polymers.

Producción Científica | This work discusses hydrolysis of defatted grape in supercritical water (SCW) at 380 °C and 260 bar from 0.18 s to 1 s focusing attention to sugars recovery in the liquid phase of the product and detailed characterization of remaining solid phase enriched in polyaromatics (e.g. lignin, flavonoids, etc.). After the longest reaction time of 1 s, 56% of carbohydrates could be recovered in the liquid phase, as a result of carbohydrate hydrolysis. The high content of insoluble lignin in biomass (36%), acts as a mass transfer limitation and presents an important feature in the hydrolysis process, slowing down the conversion of carbohydrate fraction, as after the maximum time of 1s, 10% of carbohydrates still remained in the solid phase. Milled wood lignin, extracted from biomass and dioxane extract from the solid phase were characterized in order to understand the main structural changes during the SCW hydrolysis process. Dioxane (80%) extraction of solids produces a very complex mixture of lipophilic extractives, flavonoids and lignin with a certain amount of chemically linked carbohydrates. 2D NMR analysis of dioxane extract shows remarkably subtle changes in the amounts of main lignin moieties (β-O-4′, β-β’ (resinol) and β-5 (phenylcoumaran)). This subtle change of the main lignin structures is an important feature in the further valorisation of this sulfur-free lignin residue. | Ministerio de Ciencia, Innovación y Universidades - Fondo Europeo de Desarrollo Regional (projects CTQ2016-79777-R and PID2019-105975 GB-I00) | Junta de Castilla y León - Fondo Europeo de Desarrollo Regional (project VA277P18)

This work discusses hydrolysis of defatted grape in supercritical water (SCW) at 380 °C and 260 bar from 0.18 s to 1 s focusing attention to sugars recovery in the liquid phase of the product and detailed characterization of remaining solid phase enriched in polyaromatics (e.g. lignin, flavonoids, etc.). After the longest reaction time of 1 s, 56% of carbohydrates could be recovered in the liquid phase, as a result of carbohydrate hydrolysis. The high content of insoluble lignin in biomass (36%), acts as a mass transfer limitation and presents an important feature in the hydrolysis process, slowing down the conversion of carbohydrate fraction, as after the maximum time of 1s, 10% of carbohydrates still remained in the solid phase. Milled wood lignin, extracted from biomass and dioxane extract from the solid phase were characterized in order to understand the main structural changes during the SCW hydrolysis process. Dioxane (80%) extraction of solids produces a very complex mixture of lipophilic extractives, flavonoids and lignin with a certain amount of chemically linked carbohydrates. 2D NMR analysis of dioxane extract shows remarkably subtle changes in the amounts of main lignin moieties (β-O-4′, β-β’ (resinol) and β-5 (phenylcoumaran)). This subtle change of the main lignin structures is an important feature in the further valorisation of this sulfur-free lignin residue.

Biopolymers of gellan gum (G), 2-hydroxyethyl cellulose (HEC), and lignin (L)-based binary and ternary sustainable composites were prepared for food packaging and biomedical application. The composite films were flexible and transparent or translucent with slight brown in color. The incorporation of lignin considerably improved the thermal and mechanical and hydrophobic properties of the composite films. The addition of 10 wt% of lignin to the composites increased the tensile strength by 54.3% and 59.2% respectively. The prepared lignin-based composite films showed high ultraviolet (UV) protection, with almost 100% protection against UVB (280–320 nm) and 90% against UVA (320–400 nm). The surface hydrophobicity of the composite films increased with the addition of lignin. The binary and ternary composites containing 1, 5, and 10 wt% lignin exhibited excellent radical scavenging activities. The gellan gum/HEC/lignin based composite films achieved the best biocompatibility. The obtained composites showed efficient antioxidant and non-cytotoxic activities, although there was no remarkable antimicrobial activity.