Enzymatic preparation of mushroom dietary fibre: A comparison between analytical and industrial enzymes.
Wong, K. H. & Cheung, P. C. K. (2009). Food Chemistry, 115(3), 795-800.
A comparative study on preparing dietary fibres (DFs) from three mushroom sclerotia, namely, Pleurotus tuber-regium (PTR), Polyporus rhinocerus (PR) and Wolfiporia cocos (WC), using analytical or industrial enzymes (including α-amylase, protease and amyloglucosidase), was conducted. Apart from enzyme activity and purity, their effects on the yield of sclerotial DF as well as its major components, such as β-glucans, chitin and resistant glycogen (RG), were investigated and compared. The activities of all industrial enzymes were significantly lower than those of their corresponding analytical ones, except for the Fungamyl® Super MA, which had the highest α-amylase activity (6395 U/g). However, this fungal α-amylase was less able to digest the three sclerotial glycogens when compared with the bacterial alternatives. Amongst all tested enzymes, only analytical and industrial amyloglucosidases were found to have significant amount of contaminating cellulase (7.05–7.07 U/ml) and lichenase (4.62–4.67 U/ml) activities, which would cause endo-depolymerization of the β-glucan-type cell wall components (3.39% reduction in glucose residue after RG correction) of the PTR, leading to a marked α-amylase hydrolysis of its otherwise physically-inaccessible cytoplasmic glycogen (20.3% reduction in RG content). Commercial production of the three novel sclerotial DFs, using the industrial enzymes, would be feasible since, in addition to their economic advantage, both the yield (PTR: 81.2%; PR: 86.5%; WC: 96.2% of sample DM) and total non-starch polysaccharide contents (PTR: 88.0%; PR: 92.5%; WC: 91.1% DF-rich materials of DM) of their resulting sclerotial DFs were comparable to the levels of those prepared using analytical enzymes.
Role of (1,3)(1,4) β-glucan in cell walls: Interaction with cellulose.
Kiemle, S. N., Zhang, X., Esker, A. R., Toriz, G., Gatenholm, P. & Cosgrove, D. J. (2014). Biomacromolecules, 15(5), 1727-1736.
(1,3)(1,4)-β-D-Glucan (mixed-linkage glucan or MLG), a characteristic hemicellulose in primary cell walls of grasses, was investigated to determine both its role in cell walls and its interaction with cellulose and other cell wall polysaccharides in vitro. Binding isotherms showed that MLG adsorption onto microcrystalline cellulose is slow, irreversible, and temperature-dependent. Measurements using quartz crystal microbalance with dissipation monitoring showed that MLG adsorbed irreversibly onto amorphous regenerated cellulose, forming a thick hydrogel. Oligosaccharide profiling using endo-(1,3)(1,4)-β-glucanase indicated that there was no difference in the frequency and distribution of (1,3) and (1,4) links in bound and unbound MLG. The binding of MLG to cellulose was reduced if the cellulose samples were first treated with certain cell wall polysaccharides, such as xyloglucan and glucuronoarabinoxylan. The tethering function of MLG in cell walls was tested by applying endo-(1,3)(1,4)-β-glucanase to wall samples in a constant force extensometer. Cell wall extension was not induced, which indicates that enzyme-accessible MLG does not tether cellulose fibrils into a load-bearing network.
An ancient family of lytic polysaccharide monooxygenases with roles in arthropod development and biomass digestion.
Sabbadin , F., Hemsworth, G. R., Ciano, L., Henrissat, B., Dupree, P., Tryfona, T., Marques, R. D. S., Sweeney, S. T., Besser, K., Elias, L., Pesante, G., Li, Y., Dowle, A. A., Bates, R., Gomez, L. D., Simister, R., Davies, G. J., Walton, P. H., Bruce, N. C., McQueen-Mason, S. J. (2018). Nature Communications, In Press.
Thermobia domestica belongs to an ancient group of insects and has a remarkable ability to digest crystalline cellulose without microbial assistance. By investigating the digestive proteome of Thermobia, we have identified over twenty members of an uncharacterized family of lytic polysaccharide monooxygenases (LPMOs). We show that this LPMO family spans across several clades of the Tree of Life, is of ancient origin and was recruited by early arthropods with possible roles in remodelling endogenous chitin scaffolds during development and metamorphosis. Based on our in-depth characterization of Thermobia’s LPMOs, we propose that diversification of these enzymes towards cellulose digestion might have endowed ancestral insects with an effective biochemical apparatus for biomass degradation, allowing the early colonization of land during the Paleozoic Era. The vital role of LPMOs in modern agricultural pests and disease vectors offers new opportunities to help tackle global challenges in food security and the control of infectious diseases.