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Lignin has interesting functionalities to be exploited in adhesives for medicine, foods and textiles. Nanoparticles (NPs) < 100 nm coated with poly (L-lysine), PL and poly(L-glutamic acid) PGA were prepared from the laccase treated lignin to coat nanocellulose fibrils (CNF) with heat. NPs ca. 300 nm were prepared, β-casein coated and cross-linked with transglutaminase (Tgase) to agglutinate chamois. Size exclusion chromatography (SEC) and Fourier-transform infrared (FTIR) spectroscopy were used to characterize polymerized lignin, while zeta potential and dynamic light scattering (DLS) to ensure coating of colloidal lignin particles (CLPs). Protein adsorption on lignin was studied by quartz crystal microbalance (QCM). Atomic force microscopy (AFM) was exploited to examine interactions between different polymers and to image NPs with transmission electron microscopy (TEM). Tensile testing showed, when using CLPs for the adhesion, the stress improved ca. 10 and strain ca. 6 times compared to unmodified Kraft. For the β-casein NPs, the values were 20 and 8, respectively, and for the β-casein coated CLPs between these two cases. When NPs were dispersed in adhesive formulation, the increased Young’s moduli confirmed significant improvement in the stiffness of the joints over the adhesive alone. Exploitation of lignin in nanoparticulate morphology is a potential method to prepare bionanomaterials for advanced applications.

The formation of disulfide bonds in proteins and small molecules can greatly affect their functionality. Sulfhydryl oxidases (SOXs) are enzymes capable of oxidising the free sulfhydryl groups in proteins and thiol-containing small molecules by using molecular oxygen as an electron acceptor. SOXs have been isolated from the intracellular compartments of many organisms, but also secreted SOXs are known. These latter enzymes are generally active on small compounds and their physiological role is unknown, whereas the intracellular enzymes prefer proteins as substrates and are involved in protein folding. An increasing number of scientific publications and patent applications on SOXs have been published in recent years. The present mini-review provides an up-to-date summary of SOXs from various families, their production and their actual or suggested applications. The sequence features and domain organisation of the characterised SOXs are reviewed, and special attention is paid to the physicochemical features of the enzymes. A review of patents and patent applications regarding this class of enzymes is also provided.

Sulfhydryl oxidases (SOX) are FAD-dependent enzymes capable of oxidising free thiol groups and forming disulphide bonds. Although the quantity of scientific papers and suggested applications for SOX is constantly increasing, only a limited number of microbial SOX have been reported and are commercially available. Hence, the aim of this study was to develop a fast and reliable qualitative plate test for screening novel secreted fungal SOX. The screening was based on the Ellman's reagent, i.e. 5,5'-dithiobis[2-nitrobenzoic acid]. Altogether, 32 fungal strains from an in-house culture collection were screened. A total of 13 SOX-producing strains were found positive in the plate test screen. The novel SOX producers were Aspergillus tubingensis, Chaetomium globusum, Melanocarpus albomyces, Penicillium aurantiogriseum, Penicillium funiculosum, Coniophora puteana and Trametes hirsuta. Six of the discovered SOX were partially characterised by determination of isoelectric point, pH optimum and substrate specificity. A. tubingensis was identified as the most efficient novel SOX producer.