Self-Assembly of Rod-Coil Bottlebrush Copolymers into Degradable Nanodiscs with a UV-Triggered Self-Immolation Process

Polymer nanodiscs, especially with stimuli-responsive features, represent an unexplored frontier in the nanomaterial landscape. Such 2D nanomaterials are considered highly promising for advanced biomedicine applications. Herein, we designed a rod-coil copolymer architecture based on an amphiphilic, tadpole-like bottlebrush copolymer, which can directly self-assemble into core-shell nanodiscs in an aqueous environment. As the bottlebrush side chains are made of amorphous, UV-responsive poly(ethyl glyoxylate) (PEtG) chains, they can undergo rapid end-to-end self-immolation upon light irradiation. This triggered nanodisc disassembly can be used to boost small molecule release from the nanodisc core, which is further aided by a morphological change from discs to spheres.

Depolymerisation of Kraft Lignin by Tailor-Made Alkaliphilic Fungal Laccases

Lignins released in the black liquors of kraft pulp mills are an underutilised source of aromatics. Due to their phenol oxidase activity, laccases from ligninolytic fungi are suitable biocatalysts to depolymerise kraft lignins, which are characterised by their elevated phenolic content. However, the alkaline conditions necessary to solubilise kraft lignins make it difficult to use fungal laccases whose activity is inherently acidic. We recently developed through enzyme-directed evolution high-redox potential laccases active and stable at pH 10. Here, the ability of these tailor-made alkaliphilic fungal laccases to oxidise, demethylate, and depolymerise eucalyptus kraft lignin at pH 10 is evidenced by the increment in the content of phenolic hydroxyl and carbonyl groups, the methanol released, and the appearance of lower molecular weight moieties after laccase treatment. Nonetheless, in a second assay carried out with higher enzyme and lignin concentrations, these changes were accompanied by a strong increase in the molecular weight and content of β-O-4 and β-5 linkages of the main lignin fraction, indicating that repolymerisation of the oxidised products prevails in one-pot reactions. To prevent it, we finally conducted the enzymatic reaction in a bench-scale reactor coupled to a membrane separation system and were able to prove the depolymerisation of kraft lignin by high-redox alkaliphilic laccase.

Analytical Method Cluster Development for Comprehensive Characterisation of Suberinic Acids Derived from Birch Outer Bark

Suberin is a complex polyester biopolymer, and it is practically impossible to estimate the real content of suberin in suberised plant tissues. This indicates the importance of the development of instrumental analytical methods for the comprehensive characterisation of suberin derived from plant biomass for the successful integration of suberinic products into biorefinery production chains. In this study, we optimised two GC-MS methods-one with direct sylilation, and the second with additional depolymerisation, using GPC methods with RI detector and polystyrene calibration and with a three-angle light scattering detector and an eighteen-angle light scattering detector. We also performed MALDI-Tof analysis for non-degraded suberin structure determination. We characterised suberinic acid (SA) samples obtained from birch outer bark after alkaline depolymerisation. The samples were particularly rich in diols, fatty acids and their esters, hydroxyacids and their corresponding esters, diacids and their corresponding esters, as well as extracts (mainly betulin and lupeol) and carbohydrates. To remove phenolic-type admixtures, treatment with ferric chloride (FeCl₃) was used. The SA treatment with FeCl₃ allows the possibility to obtain a sample that has a lower content of phenolic-type compounds and a lower molecular weight than an untreated sample. It was possible to identify the main free monomeric units of SA samples by GC-MS system using direct silylation. By performing an additional depolymerisation step before silylation, it was possible to characterise the complete potential monomeric unit composition in the suberin sample. For the molar mass distribution determination, it is important to perform GPC analysis. Even though chromatographic results can be obtained using a three- laser MALS detector, they are not fully correct because of the fluorescence of the SA samples. Therefore an 18-angle MALS detector with filters was more suitable for SA analysis. MALDI-Tof analysis is a great tool for the polymeric compound structural identification, which cannot be done using GC-MS. Using the MALDI data, we discovered that the main monomeric units that makes up the SA macromolecular structure are octadecanedioic acid and 2-(1,3-dihydroxyprop-2-oxy)decanedioic acid. This corresponds with GC-MS results, showing that after depolymerisation hydroxyacids and diacids were the dominant type of compounds found in the sample.

Evaluation of Antibacterial and Antifungal Properties of Low Molecular Weight Chitosan Extracted from Hermetia illucens Relative to Crab Chitosan

This study shows the research on the depolymerisation of insect and crab chitosans using novel enzymes. Enzyme preparations containing recombinant chitinase Chi 418 from Trichoderma harzianum, chitinase Chi 403, and chitosanase Chi 402 from Myceliophthora thermophila, all belonging to the family GH18 of glycosyl hydrolases, were used to depolymerise a biopolymer, resulting in a range of chitosans with average molecular weights (M_w) of 6–21 kDa. The depolymerised chitosans obtained from crustaceans and insects were studied, and their antibacterial and antifungal properties were evaluated. The results proved the significance of the chitosan’s origin, showing the potential of Hermetia illucens as a new source of low molecular weight chitosan with an improved biological activity.

Ambient-Pressured Acid-Catalysed Ethylene Glycol Organosolv Process: Liquefaction Structure-Activity Relationships from Model Cellulose-Lignin Mixtures to Lignocellulosic Wood Biomass

Raising the awareness of carbon dioxide emissions, climate global warming and fossil fuel depletion has renewed the transition towards a circular economy approach, starting by addressing active bio-economic precepts that all portion amounts of wood are valorised as products. This is accomplished by minimizing residues formed (preferably no waste materials), maximizing reaction productivity yields, and optimising catalysed chemical by-products. Within framework structure determination, the present work aims at drawing a parallel between the characterisation of cellulose–lignin mixture (derived system model) liquefaction and real conversion process in the acidified ethylene glycol at moderate process conditions, i.e., 150 °C, ambient atmospheric pressure and potential bio-based solvent, for 4 h. Extended-processing liquid phase is characterized considering catalyst-transformed reactant species being produced, mainly recovered lignin-based polymer, by quantitative 31P, 13C and 1H nuclear magnetic resonance (NMR) spectroscopy, as well as the size exclusion- (SEC) or high performance liquid chromatography (HPLC) separation for higher or lower molecular weight compound compositions, respectively. Such mechanistic pathway analytics help to understand the steps in mild organosolv biopolymer fractionation, which is one of the key industrial barriers preventing a more widespread manufacturing of the biomass-derived (hydroxyl, carbonyl or carboxyl) aromatic monomers or oligomers for polycarbonates, polyesters, polyamides, polyurethanes and (epoxy) resins.

Valorisation of plastic waste via metal-catalysed depolymerisation

Metal-catalysed depolymerisation of plastics to reusable building blocks, including monomers, oligomers or added-value chemicals, is an attractive tool for the recycling and valorisation of these materials. The present manuscript shortly reviews the most significant contributions that appeared in the field within the period January 2010–January 2020 describing selective depolymerisation methods of plastics. Achievements are broken down according to the plastic material, namely polyolefins, polyesters, polycarbonates and polyamides. The focus is on recent advancements targeting sustainable and environmentally friendly processes. Biocatalytic or unselective processes, acid–base treatments as well as the production of fuels are not discussed, nor are the methods for the further upgrade of the depolymerisation products.

Glycolysis of Poly(Ethylene Terephthalate) Using Biomass-Waste Derived Recyclable Heterogeneous Catalyst

Plastic production has increased by almost 200-fold annually from 2 million metric tons per year in 1950s to 359 million metric tons in 2018. With this rapidly increasing production, plastic pollution has become one of the most demanding environmental issues and tremendous efforts have been initiated by the research community for its disposal. In this present study, we reported for the first time, a biomass-waste-derived heterogeneous catalyst prepared from waste orange peel for the depolymerisation of poly(ethylene terephthalate) (PET) to its monomer, bis(2-hydroxyethyl terephthalate) (BHET). The prepared orange peel ash (OPA) catalyst was well-characterised using techniques such as IR, inductively coupled plasma (ICP)-OES (Optical Emission Spectrometry), XRD, X-ray fluorescence (XRF), SEM, energy-dispersive X-ray spectroscopy (EDX), TEM, BET (Brunauer-Emmett-Teller) and TGA. The catalyst was found to be composed of basic sites, high surface area, and a notable type-IV N₂ adsorption–desorption isotherm indicating the mesoporous nature of the catalyst, which might have eventually enhanced the rate of the reaction as well as the yield of the product. The catalyst completely depolymerises PET within 90 min, producing 79% of recrystallised BHET. The ability of reusing the catalysts for 5 consecutive runs without significant depreciation in the catalytic activity and its eco- and environmental-friendliness endorses this protocol as a greener route for PET recycling.

λ-Carrageenan Oligosaccharides of Distinct Anti-Heparanase and Anticoagulant Activities Inhibit MDA-MB-231 Breast Cancer Cell Migration

In tumor development, the degradation of heparan sulfate (HS) by heparanase (HPSE) is associated with cell-surface and extracellular matrix remodeling as well as the release of HS-bound signaling molecules, allowing cancer cell migration, invasion and angiogenesis. Because of their structural similarity with HS, sulfated polysaccharides are considered a promising source of molecules to control these activities. In this study, we used a depolymerisation method for producing λ-carrageenan oligosaccharides (λ-CO), with progressive desulfation over time. These were then used to investigate the influence of polymeric chain length and degree of sulfation (DS) on their anti-HPSE activity. The effects of these two features on λ-CO anticoagulant properties were also investigated to eliminate a potential limitation on the use of a candidate λ-CO as a chemotherapeutic agent. HPSE inhibition was mainly related to the DS of λ-CO, however this correlation was not complete. On the other hand, both chain length and DS modulated λ-CO activity for factor Xa and thrombin IIa inhibition, two enzymes that are involved in the coagulation cascade, and different mechanisms of inhibition were observed. A λ-carrageenan oligosaccharide of 5.9 KDa was identified as a suitable anticancer candidate because it displayed one of the lowest anticoagulant properties among the λ-CO produced, while showing a remarkable inhibitory effect on MDA-MB-231 breast cancer cell migration.

Controlling the Molecular Weight of Lignosulfonates by an Alkaline Oxidative Treatment at Moderate Temperatures and Atmospheric Pressure: A Size-Exclusion and Reverse-Phase Chromatography Study

The molecular weights of lignosulfonates (LSs) are modified by a rather simple process involving an alkaline oxidative treatment at moderate temperatures (70-90 °C) and atmospheric pressure. Starting from LSs with an average molecular weight of 90,000 Da, and using such a treatment, one can prepare controlled molecular weight LSs in the range of 30,000 to 3500 Da based on the average mass molecular weight. The LS depolymerisation was monitored via reverse-phase and size-exclusion chromatography. It has been shown that the combination of O₂, H₂O₂ and Cu as a catalyst in alkaline conditions at 80 °C induces a high LS depolymerisation. The depolymerisation was systemically accompanied by a vanillin production, the yields of which reached 1.4 wt % (weight percentage on LS raw basis) in such conditions. Also, the average molecular weight and vanillin concentration were correlated and depended linearly on the temperature and reaction duration.

Catalytic depolymerization of lignin in supercritical ethanol

One-step valorization of soda lignin in supercritical ethanol using a CuMgAlOx catalyst results in high monomer yield (23 wt%) without char formation. Aromatics are the main products. The catalyst combines excellent deoxygenation with low ring-hydrogenation activity. Almost half of the monomer fraction is free from oxygen. Elemental analysis of the THF-soluble lignin residue after 8 h reaction showed a 68% reduction in O/C and 24% increase in H/C atomic ratios as compared to the starting Protobind P1000 lignin. Prolonged reaction times enhanced lignin depolymerization and reduced the amount of repolymerized products. Phenolic hydroxyl groups were found to be the main actors in repolymerization and char formation. 2D HSQC NMR analysis evidenced that ethanol reacts by alkylation and esterification with lignin fragments. Alkylation was found to play an important role in suppressing repolymerization. Ethanol acts as a capping agent, stabilizing the highly reactive phenolic intermediates by O-alkylating the hydroxyl groups and by C-alkylating the aromatic rings. The use of ethanol is significantly more effective in producing monomers and avoiding char than the use of methanol. A possible reaction network of the reactions between the ethanol and lignin fragments is discussed.