Malwina Michalak
Technical University of Denmark
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Featured researches published by Malwina Michalak.
Enzyme and Microbial Technology | 2012
Malwina Michalak; Lise Vestergaard Thomassen; Henna Röytiö; Arthur C. Ouwehand; Anne S. Meyer; Jørn Dalgaard Mikkelsen
Potato pulp is a high-volume side-stream from industrial potato starch manufacturing. Enzymatically solubilized β-1,4-galactan-rich potato pulp polysaccharides of molecular weights >100 kDa (SPPP) are highly bifidogenic in human fecal sample fermentations in vitro. The objective of the present study was to use potato β-1,4-galactan and the SPPP as substrates for enzymatic production of potentially prebiotic compounds of lower and narrower molecular weight. A novel endo-1,4-β-galactanase from Emericella nidulans (anamorph Aspergillus nidulans), GH family 53, was produced in a recombinant Pichia pastoris strain. The enzyme was purified by Cu(2+) affinity chromatography and its optimal reaction conditions were determined to pH 5 and 49°C via a statistical experimental design. The specific activity of the E. nidulans enzyme expressed in P. pastoris was similar to that of an endo-1,4-β-galactanase from Aspergillus niger used as benchmark. The E. nidulans enzyme expressed in P. pastoris generated a spectrum poly- and oligo-saccharides which were fractionated by membrane filtration. The potential growth promoting properties of each fraction were evaluated by growth of beneficial gut microbes and pathogenic bacteria. All the galactan- and SPPP-derived products promoted the growth of probiotic strains of Bifidobacterium longum and Lactobacillus acidophilus and generally did not support the propagation of Clostridium perfringens in single culture fermentations. Notably the growth of B. longum was significantly higher (p<0.05) or at least as good on galactan- and SPPP-derived products as fructooligosaccharides (FOS). Except in one case these products did not support the growth of the pathogen Cl. perfringens to any significant extent.
PLOS ONE | 2014
Carsten Jers; Malwina Michalak; Dorte Møller Larsen; Kasper Planeta Kepp; Haiying Li; Yao Guo; Finn Kirpekar; Anne S. Meyer; Jørn Dalgaard Mikkelsen
This paper reports rational engineering of Trypanosoma rangeli sialidase to develop an effective enzyme for a potentially important type of reactivity: production of sialylated prebiotic glycans. The Trypanosoma cruzi trans-sialidase and the homologous T. rangeli sialidase has previously been used to investigate the structural requirements for trans-sialidase activity. We observed that the T. cruzi trans-sialidase has a seven-amino-acid motif (197–203) at the border of the substrate binding cleft. The motif differs substantially in chemical properties and substitution probability from the homologous sialidase, and we hypothesised that this motif is important for trans-sialidase activity. The 197–203 motif is strongly positively charged with a marked change in hydrogen bond donor capacity as compared to the sialidase. To investigate the role of this motif, we expressed and characterised a T. rangeli sialidase mutant, Tr13. Conditions for efficient trans-sialylation were determined, and Tr13s acceptor specificity demonstrated promiscuity with respect to the acceptor molecule enabling sialylation of glycans containing terminal galactose and glucose and even monomers of glucose and fucose. Sialic acid is important in association with human milk oligosaccharides, and Tr13 was shown to sialylate a number of established and potential prebiotics. Initial evaluation of prebiotic potential using pure cultures demonstrated, albeit not selectively, growth of Bifidobacteria. Since the 197–203 motif stands out in the native trans-sialidase, is markedly different from the wild-type sialidase compared to previous mutants, and is shown here to confer efficient and broad trans-sialidase activity, we suggest that this motif can serve as a framework for future optimization of trans-sialylation towards prebiotic production.
Acta Crystallographica Section F-structural Biology and Crystallization Communications | 2013
Harm Otten; Malwina Michalak; Jørn Dalgaard Mikkelsen; Sine Larsen
A novel Emericella nidulans endo-β-1,4-galactanase (EnGAL) demonstrates a strong capacity to generate high levels of very potent prebiotic oligosaccharides from potato pulp, a by-product of the agricultural potato-starch industry. EnGAL belongs to glycoside hydrolase family 53 and shows high (72.5%) sequence identity to an endo-β-1,4-galactanase from Aspergillus aculeatus. Diffraction data extending to 2.0 Å resolution were collected from a crystal of EnGAL grown from conditions containing 0.2 M zinc acetate. The crystal structure showed a high similarity between EnGAL and other endo-β-1,4-galactanases belonging to GH53. It also revealed 15 zinc ions bound to the protein, one of which is located in the active site, where it is coordinated by residues Glu136 and Glu246 which comprise the catalytic machinery. The majority of the zinc ions are located on the surface of the enzyme, in some cases with side chains from two different molecules as ligands, thus explaining why the presence of zinc ions was essential for crystallization.
New Biotechnology | 2014
Jesper Holck; Dorte Møller Larsen; Malwina Michalak; Haiying Li; Louise Kjærulff; Finn Kirpekar; Charlotte Held Gotfredsen; Sofia D. Forssten; Arthur C. Ouwehand; Jørn Dalgaard Mikkelsen; Anne S. Meyer
Process Biochemistry | 2014
Malwina Michalak; Dorte Møller Larsen; Carsten Jers; João Ricardo M. Almeida; Martin Willer; Haiying Li; Finn Kirpekar; Louise Kjærulff; Charlotte Held Gotfredsen; Rune Thorbjørn Nordvang; Anne S. Meyer; Jørn Dalgaard Mikkelsen
Journal of Agricultural and Food Chemistry | 2013
Hassan Ahmadi Gavlighi; Malwina Michalak; Anne S. Meyer; Jørn Dalgaard Mikkelsen
Archive | 2014
Malwina Michalak; Jørn Dalgaard Mikkelsen; Gunnar Eigil Jonsson; Manuel Pinelo
DTU Sustain Conference 2014 | 2014
Jesper Holck; Birgitte Zeuner; Malwina Michalak; Yao Guo; Carsten Jers; Jørn Dalgaard Mikkelsen; Anne S. Meyer
Archive | 2014
Jørn Dalgaard Mikkelsen; Hassan Ahmadi Gavlighi; Malwina Michalak; Anne S. Meyer; Marcel Tutor Ale; Dennis S. Nielsen
Archive | 2014
Jørn Dalgaard Mikkelsen; Carsten Jers; Malwina Michalak; Kasper Planeta Kepp; Dorte Møller Larsen