Davide Beneventi’s research while affiliated with Grenoble Alpes University and other places

Nanostructured materials represent promising substrates for biocatalyst immobilization and activation. Cellulose nanocrystals (CNCs), accessible from waste and/or renewable sources, are sustainable and biodegradable, show high specific surface area for anchoring a high number of enzymatic units, and high thermal and mechanical stability. In this work, we present a holistic enzyme‐based approach to functional antibacterial materials by bioconjugation between the lysozyme from chicken egg white and enzymatic cellulose nanocrystals. The neutral CNCs were prepared by endoglucanase hydrolysis from Avicel. We explore the covalent immobilization of lysozyme on enzymatic CNCs and on their TEMPO oxidized derivatives (TO‐CNCs), comparing immobilization yields, material properties, and enzymatic activities. The materials were characterized by X‐ray diffractometry (XRD), attenuated total reflectance Fourier Transform infrared spectroscopy (ATR‐FTIR), bicinchoninic acid (BCA) assay, field‐emission scanning electron microscopy (FE‐SEM) and dynamic light scattering (DLS). We demonstrate the higher overall efficiency of the immobilization process carried out on TO‐CNCs, based on the success of covalent bonding and on the stability of the isolated bioconjugates.

The aim of the present study was to investigate the rheological properties of microfibrillated cellulose (MFC)/ lignosulfonate (LS) hydrogels and to use them in the manufacture of carbon objects by 3D printing and carbonization. For this purpose, both flow mode and thixotropic mode were used to characterize the hydrogel rheological behavior, which was subsequently used to search for formulation/processability correlations during 3D printing of square cuboids. At a concentration of 2%, MFC displayed excellent printability, i.e., shear-thinning behavior with high yield stress and a viscoelastic response to a step-down shear rate variation. The addition of LS induced a drop in the yield stress, and above an LS mass fraction of 30%, the MFC/LS hydrogels displayed an inelastic thixotropic response with a drop in printability (viz., the printed cuboids underwent a continuous deformation until spreading of the hydrogel was complete). Above 50% LS, the high viscosity slowed the flow of the MFC/LS hydrogels, and the printed cuboids had minor deformation. Freeze and air drying of cuboids printed with LS mass fractions lower than 20% and higher than 50%, respectively, allowed the cuboids to keep their original shape, and their carbonization under inert gas led to the production of highly conducting objects. In line with the high density of the air-dried samples, carbonized samples displayed an irregular structure with pores and crackles generated during drying and carbonization, whereas the freeze-dried samples had the typical lamellar structure of ice-templated materials.

Cellulose nanocrystals are an important class of bio‐based crystalline nanostructures, finding application in several technological fields, including paper and textile coating, biocomposite engineering, biocatalysts immobilization, etc. This study explores enzymatic hydrolysis of Avicel, using endoglucanase from Aspergillus niger, to find an environmentally friendly method to extract cellulose nanocrystals from cellulose sources. Enzymatic hydrolysis has the advantage of reduced energy consumption and higher environmental friendliness compared to acid hydrolysis. In this work, we report for the first time very high nanocrystals yield by combining mechanical pretreatment of the cellulose starting material with a ball miller and endoglucanase hydrolysis, as a result of an extensive optimization of reaction conditions. In particular, a ball milling pretreatment carried out for 50 minutes at 3 Hz, allowed to isolate enzymatic CNCs with 76 % yield and with crystallinity as high as 75 %. The materials were characterized by X‐Ray diffractometry, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, dynamic light scattering, zeta potential and field emission scanning electron microscopy (FE‐SEM). Their characteristics were compared with the properties of sulfated CNCs, prepared from Avicel by sulfuric acid hydrolysis. Our results are technologically relevant, as they contribute to the accessibility and sustainability of CNCs for a wide range of applications in various industries.

Abiotic 3D-printed cathodes for biofuel cells were manufactured using chitosan-cellulose nanofibres-iron doped graphene hydrogels and the cold material extrusion (MEX) 3D printing technique. The subsequent pyrolysis under ammoniac flux and in-situ n-doping of 3D cathodes led to the generation of conductive 3D electrodes with macroporosity that can be tuned by adjusting the linera infill in the 3D printing process and enhanced electrochemical activity. In-situ n-doped electrodes with 40% macroporosity provided a neat increase in specific current, i.e. from 13 µA/mg of 3D electrodes containing pre-doped graphene to 35 µA/mg of pyrolyzed ones, thus showing that MEX 3D printing followed by in-situ n-doping is a promising manufacturing process for the fabrication of high current density abiotic cathodes. Graphical abstract

3D printing has recently triggered huge attention in several fields such as construction, artificial tissue engineering, food fabrication, wearable electronics, and electrochemical energy storage. This work investigates the fabrication of a 3D-printed abiotic cathode for implantable glucose/oxygen biofuel cells. The ink formulation was optimized to get printable ink with high electro-catalytic activity. Electrode macro porosity was screened in order to identify the better compromise between electrode density and electrochemical performance. A maximum current density of 260 μA/cm2 was obtained with cylindrical electrodes with linear mesh infill and a volumic infill rate of 40%. A complete biofuel cell was assembled using a 3D-printed abiotic cathode and an enzymatic anode in the form of a compressed pellet showing maximum power and current densities of 80 μW/cm2 and 320 μA/cm2, respectively. Moreover, the hybrid biofuel cell was implanted in the intraabdominal region of a rat for three months and after cell explantation, the abiotic cathode displayed a 50% decrease in the current density while the enzymatic anode did not display any residual activity. The 3D printed electrode displayed a 2–3.6-fold increase in current density when compared to homolog 2D electrodes.

3D cheap, lightweight and robust cellulosic parts can be obtained via extrusion of a cellulosic aqueous paste followed by air-drying. During the air-drying step, an anisotropic shrinkage occurs. The objective of this study is to characterize the macro and mesoscale phenomena occurring during the drying process. We used sub-minute laboratory X-ray microtomography during air-drying tests combined with advanced image analysis including Digital Volume Correlation to reveal the mechanisms that took place at the sample and at the filament scales. This allowed the qualitative and quantitative analysis of the structural and kinematical changes occurring during the air-drying. The macroscopic anisotropic shrinkage of the structure is associated with a decrease of the solid fraction of the cube and a decrease of the volume of the central pore, a decrease of the number and of the volume of the inter-filament and intra-filament pores, a change of the shape and dimensions of the filaments cross section. We observed delamination effects, increase of the number of inter and intra filament pores. These results complete the analysis commonly carried out at the macroscale and are necessary to build a model for the prediction of drying mechanisms of 3D printed part of cellulose and to propose more accurate compensation strategies.

This study aims to develop a green composite based on two biomass‐based components via the curing of an oligomeric furfuryl resin coupled with 18–31 wt% cellulose powder. The curing was performed in an atmospheric pressure open air oven. The chemical composition of the used pre‐polymer was characterized with Fourier transform infrared and NMR spectroscopy and its curing reaction was followed by differential scanning calorimetry. The final cured composites were characterized to investigate the effect of cellulose addition on their morphology, dimensional stability, and thermo‐mechanical performances. The manufactured composite showed good thermal stability up to 200°C with a storage modulus higher than 2 GPa, and a mass loss under 3%. Moreover, the filler improved the composite dimensional stability upon crosslinking by 38% and the mechanical performances with respectively 15% and 40% increase in the Young's and flexural moduli. By the same token, cellulose prevented the typical foaming of poly(furfuryl alcohol) resins crosslinked at high temperature and low pressure. Preliminary tests highlighted the excellent processability of the developed composite, which was used to manufacture a static demonstrator coupling different fabrication techniques, that is, 3D printing (direct ink writing), high temperature compression molding and CNC machining.