Abstract:
:Co-Immobilization of dextransucrase (DS) and dextranase (DN) into calcium alginate includes the co-entrapment of soluble DS and adsorbed DN. DS converts sucrose into dextran, which is the substrate for DN, so that isomalto-oligosaccharides (IMOs) are follow-up products of dextran hydrolysis. The boundary conditions for the successful preparation are investigated with respect to choice of DN adsorbate, surface modifications using blotting agents and optimal enzyme activity ratios. Further, repetitive batch experiments suggest the selection of medium activity ratios for continuous use (0.3 U(DN)U(-1) (DS), e.g.). Product formation at various cosubstrate:substrate concentrations as well as at different DN:DS ratios are discussed. Moreover, the complexity of the bi-enzymatic system can be reduced considering the molar ratios of cosubstrate:substrate (glucose:sucrose). Based on these factors, a mechanistic kinetic model is developed, which distinguishes the corresponding contributions of the two enzymes upon overall product formation. In general, at low glucose:sucrose ratios isomaltose synthesis is featured primarily by DN action. Yet with increasing amounts of glucose both the quantity and quality of DN substrate changes, so that its contribution to product formation decreases in an exponential manner; still the overall product yield continuously increases due to enhanced DS contribution.
journal_name
Biotechnol Bioengjournal_title
Biotechnology and bioengineeringauthors
Erhardt FA,Kügler J,Chakravarthula RR,Jördening HJdoi
10.1002/bit.21810subject
Has Abstractpub_date
2008-07-01 00:00:00pages
673-83issue
4eissn
0006-3592issn
1097-0290journal_volume
100pub_type
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