Identification of in situ lignin strength based on micropillar compression and micromechanical modeling of wood cell walls

Many biological materials feature a hierarchical architecture with remarkable mechanical properties combining low weight with both toughness and strength. In order to better understand the mechanisms leading to this unusual combination of traits, structure-property relationships have to be assessed on all length scales. Wood is such a hierarchical material. Its cell walls feature semi-crystalline cellulose fibrils embedded in an amorphous polymer network that are aligned at an angle to the cell main axis resembling a fiber reinforced composite. Continuum micromechanics can predict mechanical behavior on a higher length scale based on the composition, microstructure, and properties of the individual phases. However, the experimental data for yield properties at the microscale is sparse making an identification of phase properties and validation of yield predictions difficult. Specifically, the lignin shear strength in wood remains to be measured, which proves to be difficult due to the intermixed nature of the polymer network and the small length scales involved. Inverse determination of phase properties from experiments on a higher length scale is possible using continuum micromechanics, if composition, microstructure, and boundary conditions are sufficiently well understood. An experimental setup for micromechanical testing with well-defined boundary conditions is micropillar compression. Micron sized pillars are eroded from bulk cell wall material using a focused ion beam and compressed uniaxially using a flat punch indenter. Due to the mostly homogeneous and uniaxial loading conditions, the experimental data may be combined with micromechanical modeling to access phase properties at a lower length scale. The aim of this work was to perform micromechanical tests leading to homogeneous and uniaxial stress fields on a single cell wall layer for normal (NW) and compression wood (CW) of Norway spruce. Additionally, the chemical composition was determined by wet chemical analysis and the cellulose fibril angle distribution was measured using wide angle XRD. Subsequently, a continuum micromechanics model for elastic limit states was used to explain the measured properties and to relate them to species-independent phase properties on a lower length scale, more specifically the lignin yield stress. The study demonstrates a novel approach for measuring phase properties of inhomogeneous materials by a combination of continuum micromechanical modeling and micropillar compression experiments inside a scanning electron microscope under controlled conditions. The mostly homogeneous and uniaxial stress state in this experimental setup allows to identify yield stresses at the microscale and to assess phase properties on a lower length scale with high accuracy and reproducibility if the microstructure and the inelastic deformation mechanisms of the tested material are well understood. This could be an interesting approach for validating multiscale models or identifying phase properties for other nanostructured materials in the future

Self-Immobilizing Biocatalysts Maximize Space–Time Yields in Flow Reactors

Maximizing space–time yields (STY) of biocatalytic flow processes is essential for the establishment of a circular biobased economy. We present a comparative study in which different biocatalytic flow reactor concepts were tested with the same enzyme, the (R)-selective alcohol dehydrogenase from Lactobacillus brevis (LbADH), that was used for stereoselective reduction of 5-nitrononane-2,8-dione. The LbADH contained a genetically encoded streptavidin (STV)-binding peptide to enable self-immobilization on STV-coated surfaces. The purified enzyme was immobilized by physisorption or chemisorption as monolayers on the flow channel walls, on magnetic microbeads in a packed-bed format, or as self-assembled all-enzyme hydrogels. Moreover, a multilayer biofilm with cytosolic-expressed LbADH served as a whole-cell biocatalyst. To enable cross-platform comparison, STY values were determined for the various reactor modules. While mono- and multilayer coatings of the reactor surface led to STY 450). The latter modules could be operated for prolonged times (>6 days). Given that our approach should be transferable to other enzymes, we anticipate that compartmentalized microfluidic reaction modules equipped with self-immobilizing biocatalysts would be of great utility for numerous biocatalytic and even chemo-enzymatic cascade reactions under continuous flow conditions

Glycolipids produced by Rouxiella sp. DSM 100043 and isolation of the biosurfactants via foam-fractionation

Additional file 1. Table S1, Figure S1–Figure S3: Mass spectrometry data and plots of purified foam extracts of Rouxiella sp. DSM 100043. Figure S4: Full NMR spectra of Rouxiella sp. DMS 100043 glycolipids present in fractions 64-65

Machine-assisted cultivation and analysis of biofilms

Biofilms are the natural form of life of the majority of microorganisms. These multispecies consortia are intensively studied not only for their effects on health and environment but also because they have an enormous potential as tools for biotechnological processes. Further exploration and exploitation of these complex systems will benefit from technical solutions that enable integrated, machine-assisted cultivation and analysis. We here introduce a microfluidic platform, where readily available microfluidic chips are connected by automated liquid handling with analysis instrumentation, such as fluorescence detection, microscopy, chromatography and optical coherence tomography. The system is operable under oxic and anoxic conditions, allowing for different gases and nutrients as feeding sources and it offers high spatiotemporal resolution in the analysis of metabolites and biofilm composition. We demonstrate the platform’s performance by monitoring the productivity of biofilms as well as the spatial organization of two bacterial species in a co-culture, which is driven by chemical gradients along the microfluidic channel

Contractual dependencies: Disability and the bureaucracies of begging in Kinshasa, Democratic Republic of Congo

One of the most conspicuous livelihood strategies for physically disabled people in Kinshasa, Democratic Republic of Congo, is a particular style of begging known locally as “doing documents.” Confronted with the stigma of begging, disabled beggars create documents in an attempt to legitimize and regulate begging through formalization and bureaucracy, presenting their relationship with donors as NGO fund‐raising and government tax‐collecting. The dynamics of petitioning for these “contractual dependencies” provide a nuanced perspective on desired dependencies: dependencies can be presented in multiple ways, and people consider some dependencies more legitimate and valuable than others. Recipients are not passive but play a defining role in shaping these relationships, seeking a balance between proximity and desired distance to patrons.Economic and Social Research Council Cambridge Home and EU Scholarship Scheme Trinity College, Cambridg

Rouxiella badensis sp. nov. and Rouxiella silvae sp. nov. isolated from peat bog soil and emendation description of the genus Rouxiella

International audienceFour bacterial strains isolated from peat bog soil or swampy meadow in Baden-Württemberg (Germany) and found to have rrs sequences close to that of Rouxiella chamberiensis were compared to this species by using multi-locus sequence analysis and phenotypic tests. The four strains constituted two discrete groups (referred to as the Baden and the Silva groups) belonging to the genus Rouxiella. These groups differed in their ability to grow at 37 °C, reduce nitrate into nitrite, and to produce acid from several carbohydrates. Two novel species are, therefore, proposed: Rouxiella badensis sp. nov. for the Baden group (type strain, 323T=CIP 111153T=DSM 100043T) and Rouxiella silvae for the Silva group (type strain, 213T=CIP 111154T=DSM 103735T). The definition of the genus Rouxiellahas also been emended in order to take these two novel species into account

MOESM1 of Glycolipids produced by Rouxiella sp. DSM 100043 and isolation of the biosurfactants via foam-fractionation

Additional file 1. Table S1, Figure S1–Figure S3: Mass spectrometry data and plots of purified foam extracts of Rouxiella sp. DSM 100043. Figure S4: Full NMR spectra of Rouxiella sp. DMS 100043 glycolipids present in fractions 64-65