Search

This study deals with the comprehension of lignin partition in biphasic systems constituted of an alkaline aqueous phase containing dissolved lignin and a non-miscible alcohol phase. The main parameters studied are the botanical origin of lignins (softwood/hardwood/herbaceous), the solvent (n-butanol/n-pentanol/n-octanol) and the pH (12, 9.5, 7, 3.5). Lignin concentration is measured by UV spectroscopy to calculate partition coefficients. Lignin migration is driven by the protonation of hydroxyl phenolates at pH 12–9.5 and of carboxylates at pH 7–3.5. FTIR spectra revealed various functional groups in migrated fractions as well as their change in conformation. Notably, hydrogen bonding capacity within its chemical groups and with neighboring fragments and solvents are discussed. NMR results suggest a possibility to adjust separation conditions to tune the lignin composition including the G/S ratio and the content in specific structures (resinol, ferulate, and carbohydrate). GPC highlights a wide diversity of polymers of low molecular weight migrating at basic pH whereas increasing high molecular weight is correlated with aqueous phase acidification. The lignins seem to migrate according to similar structural features whatever the botanical origin, leading to very similar polymer distributions under given conditions. In general, butanol appears to be less selective and is able to solubilize a wide range of lignin polymers independent of the origin. This work provides valuable information regarding the separation of homogeneous lignin fractions enabling standardization of the chemical and physical properties of the lignins to increase their value and the numerous potential applications as a sustainable material.

Pretreatment is still the most expensive step in lignocellulosic biorefinery processes. It must be made cost-effective by minimizing chemical requirements as well as power and heat consumption and by using environment-friendly solvents. Deep eutectic solvents (DESs) are key, green, and low-cost solvents in sustainable biorefineries. They are transparent mixtures characterized by low freezing points resulting from at least one hydrogen bond donor and one hydrogen bond acceptor. Although DESs are promising solvents, it is necessary to combine them with an economic heating technology, such as microwave irradiation, for competitive profitability. Microwave irradiation is a promising strategy to shorten the heating time and boost fractionation because it can rapidly attain the appropriate temperature. The aim of this study was to develop a one-step, rapid method for biomass fractionation and lignin extraction using a low-cost and biodegradable solvent. In this study, a microwave-assisted DES pretreatment was conducted for 60 s at 800 W, using three kinds of DESs. The DES mixtures were facilely prepared from choline chloride (ChCl) and three hydrogen-bond donors (HBDs): a monocarboxylic acid (lactic acid), a dicarboxylic acid (oxalic acid), and urea. This pretreatment was used for biomass fractionation and lignin recovery from marine residues (Posidonia leaves and aegagropile), agri-food byproducts (almond shells and olive pomace), forest residues (pinecones), and perennial lignocellulosic grasses (Stipa tenacissima). Further analyses were conducted to determine the yield, purity, and molecular weight distribution of the recovered lignin. In addition, the effect of DESs on the chemical functional groups in the extracted lignin was determined by Fourier-transform infrared (FTIR) spectroscopy. The results indicate that the ChCl-oxalic acid mixture affords the highest lignin purity and the lowest yield. The present study demonstrates that the DES-microwave process is an ultrafast, efficient, and cost-competitive technology for lignocellulosic biomass fractionation.

Steam explosion (SE) is a versatile tool for the pretreatment of lignocellulosic plant 27 materials and the further separation of their main constitutive components, i.e. cellulose, 28 hemicellulose, lignin, etc. In this study, we propose to evaluate the effects of SE 29 treatment on the recovery of secondary metabolites. As a case study, the well-known 30 grape pomace phenolic compounds were considered. Our results demonstrate that the 31 efficiency of the steam explosion in term of yield (900 mg polyphenols per kg of dry 32 grape pomace) was relatively similar to conventional maceration methods in alcoholic 33 media (800 mg/kg). Advantages of SE compared to maceration were highlighted: the 34 process is organic solvent free, destabilize the biomass structure and release insoluble 35 bound phenolic compounds. In addition, it offers the possibility to modulate distinct 36 polyphenols profiles by modifying the process conditions.

Replacement of petroleum by other energy sources is one of the principal challenges of contemporary engineering. One of the most promising substitutes for petroleum is biomass, chemically converted into fuel. For instance, as the world's biggest producer of sugarcane, Brazil generates large quantities of agricultural residues from sugarcane cultivation which could be used to produce biofuels for transportation and aviation (i.e. jet fuel) without much difficulty. Furthermore, sugar beet industry generates important amount of waste that could be valorized into biofuels. The purpose of this article is to review the different technologies currently available for the production of biofuels via a thermochemical pathway using sugarcane bagasse and sugar beet pulp as feedstock, with specific interest in using feedstock gasification and subsequent conversion of the synthetic gas into fuel. Gasification is a longstanding process of conversion of carbonaceous material into a gaseous compound (syngas) and a solid output, called char. Several kinds of gasifiers are described, as well as the syngas cleaning-up process, and the characteristics of several processes through which syngas is converted into synthetic fuel are detailed, including Fischer-Tropsch (FT), Methanol-to-gasoline (MTG), Methanol-to-olefins (MTO) as well as pyrolysis.

Honey polyphenols have been studied with the objective of relating honeys to their floral sources. Initially synthesized by plant, these polyphenols can be found in the plant's nectar, which are collected by bees, which convert the nectar into honey. Consequently, polyphenols constitute minor components of honey. The development of a solid-phase extraction method for honey polyphenols is presented in this study. The technique employs Amberlite XAD-2 adsorbent and was tested on monofloral honeys from six different plants: acacia, chestnut, eucalyptus, thyme, sunflower, and wild carrot. Analyses were performed using high-performance liquid chromatography coupled with UV detection and mass spectrometry. Several phenolic acids and flavonoids were identified: caffeic and p-coumaric acids, quercetin, kaempferol, naringenin, chrysin, and pinocembrin. Generally, the quantity of a given polyphenol in the honey was around 0.2 mg/100 g of honey, except for chestnut honey, which contained around 3.0 mg of p-coumaric acid/100 g of honey. Analyses highlighted significant formation of cis isomers for phenolic acids during the extraction despite protection from light.