Document Detail


Oxidation of lactose to lactobionic acid by a Microdochium nivale carbohydrate oxidase: kinetics and operational stability.
MedLine Citation:
PMID:  17154316     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Oxidation of lactose to lactobionic acid by a Microdochium nivale carbohydrate oxidase was studied. The K(m)-value for lactose, obtained by a traditional enzymatic assay, was 0.066 mM at pH 6.4 and 38 degrees C. The effect of oxygen on the enzymatic rate of reaction as well as the operational stability of the enzyme was studied by performing reactions at constant pH and temperature in a stirred tank reactor. Catalase was included in all reactions to avoid inhibition and deactivation of the oxidase by hydrogen peroxide. At pH 6.4 and 38 degrees C, K(m) for oxygen was 0.97 mM, while the catalytical rate constant, k(cat), was 94 s(-1). Furthermore, we found that the operational stability of the oxidase was dependent on the type of base used for neutralization of the acid produced. Thus, when 2 M NaOH was used for neutralization of a reaction medium containing 50 mM phosphate buffer, significant deactivation of the oxidase was observed. Also, we found that the oxidase was protected against deactivation by base at high lactose concentrations. A simple model is proposed to explain the obtained results.
Authors:
Mikkel Nordkvist; Per Munk Nielsen; John Villadsen
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Biotechnology and bioengineering     Volume:  97     ISSN:  0006-3592     ISO Abbreviation:  Biotechnol. Bioeng.     Publication Date:  2007 Jul 
Date Detail:
Created Date:  2007-05-30     Completed Date:  2007-07-17     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7502021     Medline TA:  Biotechnol Bioeng     Country:  United States    
Other Details:
Languages:  eng     Pagination:  694-707     Citation Subset:  IM    
Copyright Information:
(c) 2006 Wiley Periodicals, Inc.
Affiliation:
Center for Microbial Biotechnology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
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MeSH Terms
Descriptor/Qualifier:
Ascomycota / enzymology*,  metabolism
Bioreactors / microbiology
Biotransformation
Carbohydrate Dehydrogenases / metabolism*
Disaccharides / metabolism*
Enzyme Stability
Hydrogen-Ion Concentration
Kinetics
Lactose / metabolism*
Oxidation-Reduction
Temperature
Chemical
Reg. No./Substance:
0/Disaccharides; 63-42-3/Lactose; 96-82-2/lactobionic acid; EC 1.1.-/Carbohydrate Dehydrogenases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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