A fractionation method for technical lignin was developed, combining organic solvent extraction and membrane ultrafiltration of the solvent soluble component. This method was validated on a commercial wheat straw/Sarkanda grass lignin (Protobind 1000) using 2-butanone (MEK) as the solvent for both the extraction and the ultrafiltration operations. The parent lignin and the different obtained fractions were fully characterized in terms of chemical composition and physicochemical properties by gel permeation chromatography, gas chromatography/mass spectrometry (GC/MS), pyrolysis-GC/MS, total phenol contents, ³¹P nuclear magnetic resonance (³¹P NMR), thermogravimetric analysis, differential scanning calorimetry analysis, and Fourier-transform infrared spectroscopy. The results show that the proposed process allows a straightforward recovery of the different lignin fractions as well as a selective control over their molecular mass distribution and related dependent properties. Moreover, the operating flexibility of the Soxhlet/ultrafiltration process allows the treatment of lignins from different feedstocks using the same installation just by modulating the choice of the solvent and the membrane porosity with the best characteristics. This is one of the most important features of the proposed strategy, which represents a new fractionation approach with the potential to improve lignin valorization for materials science and preparative organic chemistry applications.

The β-O-4 aryl ether linkages represent about 50% of all ethers in various lignins. At least three enzymatic steps are required to break them down: a NAD⁺-dependent C-α dehydrogenase (such as LigD and L), a glutathione lyase that releases guaiacol (i.e., a β-etherase such as LigE and F), and a glutathione-dependent lyase (i.e., LigG). In this work the LigD, L, E, F, and G from Sphingobium sp. SYK-6 were overexpressed in E. coli and purified with high yields. After characterizing the stability and kinetic properties of LigD and L on the lignin model compound GGE (1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol) and the thermostability of all five recombinant Lig enzymes, the experimental conditions for GGE bioconversion could be optimized (i.e., pH 9.0, 25 °C, ≈0.1 mg mL⁻¹ of each enzyme, and 0.5 mM racemic substrate). Under optimal conditions, and by recycling NADH using the L-lactate dehydrogenase–pyruvate system, GGE was fully converted into the final products 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)propan-1-one and guaiacol in <2 hours. Differently from what was previously reported, this result and chiral HPLC analyses demonstrated that LigG catalyzes the glutathione-dependent thioether cleavage of both β(R)- and β(S)-isomer intermediates produced by LigE and LigF β-etherases: this allowed, for the first time, reaching 100% conversion of GGE. Altogether, the recombinant five-enzyme Lig system represents a component well suited for a multienzymatic process, comprising well-known ligninolytic activities (such as peroxidases and laccases), devoted to transforming selected lignins into aromatic compounds as an alternative to the oil source.

In the present work, brewers’ spent grain (BSG), which represents the major by-product of the brewing industry, was recovered from a regional brewery and fractionated in order to obtain a complete valorization. In particular, the whole process was divided in two main parts. A first pretreatment with hot water in an autoclave allowed the separation of a solution containing the soluble proteins and sugars, which accounted for 25% of the total starting biomass. This first step allowed the preparation of a medium that was successfully employed as a valuable growing medium for different microbial fermentations, leading to valuable fungal biomass as well as triglycerides with a high content of linear or branched fatty acids, depending on the microorganism used. The solid water-insoluble residue was then submitted to a lignocellulose deep eutectic solvent-mediated fractionation, which allowed the recovery of two important main fractions: BSG cellulose and BSG lignin. The latter product was tested as potential precursor for the development of cement water reducers with encouraging results. This combination of treatments of the waste biomass appeared to be a promising sustainable strategy for the development of the full exploitation of BSG from a circular economy perspective.

This review describes the use of phospholipase D (PLD) to perform the transphosphatidylation of the most common natural phospholipid (PL), phosphatidylcholine (PC) to obtain polar head modified phospholipids with real targeted applications. The introduction of different polar heads with distinctive physical and chemical properties such as charge, polarity and dimensions allows the obtainment of very different PLs, which can be exploited in very diverse fields of application. Moreover, the inclusions of a bioactive moiety in the PL polar head constitutes a powerful tool for the stabilization and administration of active ingredients. The use of this biocatalytic approach allows the preparation of compounds which cannot be easily obtained by classical chemical methods, by using mild and green reaction conditions. PLD is a very versatile enzyme, able to catalyze both the hydrolysis of PC to choline and phosphatidic acid (PA), and the transphosphatidylation reaction in the presence of an appropriate alcohol. The yield of production of the desired product and the ratio with the collateral PA formation is highly dependent on parameters such as the nature and concentration of the alcohol and the enzymatic source. The application of PLD catalyzed transformations for the production of a great number of PLs with important uses in medical, nutraceutical and cosmetic sectors will be discussed in this work.