XXII. BIOCHEMICKÝ ZJAZD - Jesseniova lekárska fakulta

Plenary lectures
MICROBIAL XYLANASES: PROPERTIES AND APPLICATIONS
Peter Biely
Institute of Chemistry, Center of Glycomics, Slovak Academy of Sciences, Bratislava
Considerable attention of current research is devoted to development of environmentally
friendly processes for utilization of renewable resources. This effort includes also
bioconversion of the major plant hemicellulose, xylan, after cellulose, the second most
abundant polysaccharide in nature. Xylan is a heteropolysaccharide with a main chain
built of b-1,4-liked xylopyranosyl residues. Depending on a plant source the main chain is
decorated with uronic acids, arabinofuranose or esterified with acetic acid. Decomposition
of xylan in nature by microorganisms is a part of the carbon cycle and involves concerted
action of several enzymes. The enzymes attacking the xylan main chain are the depolymerizing
endo-b-1,4-xylanases and xylose-releasing b-xylosidases. The acetyl groups and
carbohydrate substituents of the main chain and are liberated with so called accessory
enzymes. The group led by the author contributed significantly to current knowledge
on the production of xylanolytic enzymes, mode of their action, substrate structure
requirements and diversity of endoxylanases and xylosidases. Important impact had
the discovery of hemicellulolytic deacetylases and introduction of efficient assays of
xylanolytic enzymes. Partial amino acid sequences of novel accessory enzymes enabled
isolation of the corresponding genes, their expression and the search for homologous
sequences in known microbial genomes. This work resulted in establishment of new
glycoside hydrolase and carbohydrate esterase families (http://www.cazy.org) with important
synthetic and biotechnological potential. Microbial enzymes hydrolyzing xylan
to oligosaccharides and fermentable sugars, and decreasing viscosity of xylan solutions
became important industrial enzymes. They found applications in the pulp and paper
industry, food industry and animal feed.
XXII. Biochemistry Congress, Martin
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