Understanding the mechanisms underlying plant biomass recalcitrance at the molecular level can only be achieved by accurate analyses of both the content and structural features of the molecules involved. Current quantification of lignin is, however, majorly based on unspecific gravimetric analysis after sulfuric acid hydrolysis. Hence, our research aimed at specific lignin quantification with concurrent characterization of its structural features. Hereto, for the first time, a polymeric 13C lignin was used as internal standard (IS) for lignin quantification via analytical pyrolysis coupled to gas chromatography with mass-spectrometric detection in selected ion monitoring mode (py-GC-SIM-MS). In addition, relative response factors (RRFs) for the various pyrolysis products obtained were determined and applied. First, 12C and 13C lignin were isolated from nonlabeled and uniformly 13C labeled wheat straw, respectively, and characterized by heteronuclear single quantum coherence (HSQC), nuclear magnetic resonance (NMR), and py-GC/MS. The two lignin isolates were found to have identical structures. Second, 13C-IS based lignin quantification by py-GC-SIM-MS was validated in reconstituted biomass model systems with known contents of the 12C lignin analogue and was shown to be extremely accurate (>99.9%, R2 > 0.999) and precise (RSD < 1.5%). Third, 13C-IS based lignin quantification was applied to four common poaceous biomass sources (wheat straw, barley straw, corn stover, and sugar cane bagasse), and lignin contents were in good agreement with the total gravimetrically determined lignin contents. Our robust method proves to be a promising alternative for the high-throughput quantification of lignin in milled biomass samples directly and simultaneously provides a direct insight into the structural features of lignin.

The article investigates the effect of taxes and social premiums on female labour supply and household income. A comparison is made between labour supply and household income between the Netherlands and the Federal Republic of Germany in 1992. A discrete choice model for labour supply is used in which taxes and social premiums are implicitly incorporated. As male labour supply is highly inelastic an individual, male chauvinist model is used. The estimated models are used to simulate the effect of the differences in the tax and social premium system on the differences in labour supply and income between both countries. The results indicate that labour force participation is higher the more individualized the system. The German system leads to a lower tax burden compared to the Dutch system. It is concluded that differences in the tax and social premium system between both countries have hardly any influence on the differences in the inequality of net household labour income. There is evidence that the German system leads to a slightly more unequal distribution of household income. It is also concluded that although the tax and social premium system does influence labour supply and income, it can be doubted whether these effects are substantial.

Summary Saprobic fungi, such as Aspergillus niger, grow as colonies consisting of a network of branching and fusing hyphae that are often considered to be relatively uniform entities in which nutrients can freely move through the hyphae. In nature, different parts of a colony are often exposed to different nutrients. We have investigated, using a multi‐omics approach, adaptation of A. niger colonies to spatially separated and compositionally different plant biomass substrates. This demonstrated a high level of intra‐colony differentiation, which closely matched the locally available substrate. The part of the colony exposed to pectin‐rich sugar beet pulp and to xylan‐rich wheat bran showed high pectinolytic and high xylanolytic transcript and protein levels respectively. This study therefore exemplifies the high ability of fungal colonies to differentiate and adapt to local conditions, ensuring efficient use of the available nutrients, rather than maintaining a uniform physiology throughout the colony.

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The willingness of highly educated workers from Germany and the Netherlands to enter the Dutch±German cross-border labour market is analysed by using survey data. The results of logit analyses show that individual predictors and factors concerning the neighbouring country are the most important determinants. Special attention is paid to the so-called`soft' factors, which are differentiated according to the nationalities involved. These factors are usually excluded from political discussion in the European Union (EU), whereas obstacles such as taxation and social security are emphasised. The results of this exploratory paper are the first steps towards a socio-economic micro-theoretic foundation of cross-border labour market behaviour, and call for further theoretical and empirical research on the determinants of cross-border labour market interactions as well as on the relation between willingness and actual mobility.

Agaricus bisporus consumes carbohydrates contained in wheat straw based compost used for commercial mushroom production. Double substituted arabinoxylan is part of the ~40% of the compost polysaccharides that are not degraded by A. bisporus during its growth and development. Genes encoding α-1,3-l-arabinofuranosidase (AXHd3) enzymes that act on xylosyl residues doubly substituted with arabinosyl residues are absent in this mushroom forming fungus. Here, the AXHd3 encoding hgh43 gene of Humicola insolens was expressed in A. bisporus with the aim to improve its substrate utilization and mushroom yield. Transformants secreted active AXHd3 in compost as shown by the degradation of double substituted arabinoxylan oligomers in an in vitro assay. However, carbohydrate composition and degree of arabinosyl substitution of arabinoxylans were not affected in compost possibly due to inaccessibility of the doubly substituted xylosyl residues.

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