New rhamnogalacturonan degrading enzymes from Aspergillus aculeatus = Nieuwe rhamnogalacturonaan afbrekende enzymen uit Aspergillus aculeatus

M. Mutter

Research output: Thesisinternal PhD, WU

Abstract

<br/>Three new rhamnogalacturonan degrading enzymes were purified from a commercial enzyme preparation, Pectinex Ultra SP, produced by the fungus <em>Aspergillus aculeatus</em> . Pectinex Ultra SP is industrially used in the mash treatment of apples and pears in juice production, increasing juice yield. Rhamnogalacturonans are highly branched polysaccharides that are part of the pectin network in the plant cell wall. The purified enzymes were characterized and appeared to be only active toward rhamnogalacturonan and not toward the well-known pectic polysaccharide homogalacturonan. Rhamnogalacturonan rhamnohydrolase is able to remove the terminal nonreducing L-rhamnose residues which are α-(1,4)-linked to D-galacturonic acid residues in rhamnogalacturonans. Rhamnogalacturonan galacturonohydrolase is an enzyme able to remove the terminal nonreducing D-galacturonic acid residues which are α-(1,2)-linked to L-rhamnose residues in rhamnogalacturonans. Both enzymes were essential analytical tools in the study of the mode of action of rhamnogalacturonan hydrolase and a third new enzyme, rhamnogalacturonan lyase, toward linear rhamnogalacturonan oligosaccharides. While rhamnogalacturonan hydrolase cleaves α-D- galacturonic acid-(1,2)-L-rhamnose linkages by hydrolysis, rhamnogalacturonan lyase cleaves the α-L- rhamnose-(1,4)-D-galacturonic acid linkages by β-elimination. Both enzymes act in an endo-fashion, with a degree of multiple attack of 4 and 2.5 respectively toward modified hairy regions of apple. From the degree of multiple attack of these endo-enzymes, combined with information on the mode of action toward linear rhamnogalacturonan oligosaccharides, it could be estimated that the average length of rhamnogalacturonan regions In modified hairy regions of apple is at least 29 sugar residues.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
Supervisors/Advisors
  • Voragen, A.G.J., Promotor, External person
  • Beldman, G., Promotor, External person
Award date15 Dec 1997
Place of PublicationS.l.
Publisher
Print ISBNs9789054857822
Publication statusPublished - 1997

Keywords

  • fermentation
  • food biotechnology
  • vegetable juices
  • fruit juices
  • aspergillus

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