Penicillin G acylase (PGA) from Escherichia coli was cross-linked with mannan dialdehydes. Conjugates were prepared with molecular masses varying from 140 to 580 kDa and containing from 18 to 50% (w/w) saccharides, the values depending on the reaction conditions (mannan/enzyme ratio), and by using mannans with different degrees of oxidation and weight-average molecular mass (M macro(w)). The pH- and thermo-stability of all preparations of glycosylated enzyme were improved remarkably, whereby the influence of the character of the linked mannan dialdehyde, its content, as well as the molecular mass of prepared glycoconjugates, on the stability of PGA, was evaluated. PGA glycosylated with the most oxidized mannan up to an M(w) of 490 kDa, containing 41% (w/w) saccharides, and retaining 90% of its original catalytic activity, showed the highest stability. The half-life of this PGA preparation increased significantly: 13-fold at pH 3, 7-fold at pH 10, and 3.5-fold at pH 8 (all at 37 degrees C), compared with the native enzyme. At higher temperatures (50 degrees C) even more significant stabilization was evident, a 16-fold increase in half-life, from 18 min to 289 min, at pH 8, being measured.
The paper deals with the influence of tree species on millipede communities (Diplopoda). The research was carried out in nine sites in the Borová hora arboretum (Zvolen town, Central Slovakia). Each studied site represents a monoculture of one of nine tree species: Betula pubescens Ehrh., Pinus sylvestris L., Larix decidua Mill., Carpinus betulus L., Abies alba Mill., Picea abies (L.) Karst., Alnus incana (L.) Moench, Populus nigra L., Ulmus laevis Pall. Millipedes were collected by pitfall trapping during vegetation periods in 2008-2011. In total, 1064 individuals of 17 species and 7 families were obtained. The results of research confirmed (i) an influence of tree species on the composition of millipede communities, (ii) a significant influence of soil nitrogen on the species richness and biodiversity, and (iii) an impact of soil pH on the species composition of these terrestrial invertebrate communities. In terms of total dynamic activity and species richness of millipedes, the most favourable conditions were revealed in the forest stands of Alnus incana, Populus nigra, Ulmus laevis and Carpinus betulus. On the contrary, the least favourable biotopes were (from both points of view) the forest stands of Betula pubescens and Larix decidua.
Three new metabolites - (-)-mitorubrinol, 2-formyl-3,5-dihydroxy-4-methylbenzoic and 2-formyl-3,5-dihydroxy-4-hydroxymethylbenzoic acids - were isolated from the culture medium of Penicillium vermiculatum DANG. Hexane extract of the mycelium contained ergosterol and esters of fatty acids, linoleic, oleic and palmitic acids being the dominating ones.
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