Abstract:
:The immobilization of dextransucrase in Ca-alginate beads relies on the close association between dextran polymer and dextransucrase. However, high amounts of dextran in the enzyme preparation drastically limit the specific activity of the immobilized enzyme (4 U/mL of alginate beads). Moreover, even in the absence of diffusion limitation at the batch conditions used, the enzyme behavior is modified by entrapment so that the dextran yield increases and the alpha-1,2 glucooligosaccharides (GOS) are produced with a lower yield (46.6% instead of 56.7%) and have a lower mean degree of polymerization than with the free dextransucrase. When the immobilized catalyst is used in a continuous reaction, the reactor flow rate necessary to obtain high conversion of the substrates is very low, leading to external diffusion resistance. As a result, dextran synthesis is even higher than in the batch reaction, and its accumulation within the alginate beads limits the operational stability of the catalyst and decreases glucooligosaccharide yield and productivity. This effect can be limited by using reactor columns with length to diameter ratio > or =20, and by optimizing the substrate concentrations in the feed solution: the best productivity obtained was 3.74 g. U(-1). h(-1), with an alpha-1,2 GOS yield of 36%.
journal_name
Biotechnol Bioengjournal_title
Biotechnology and bioengineeringauthors
Dols-Lafargue M,Willemot RM,Monsan PF,Remaud-Simeon Mdoi
10.1002/bit.1183subject
Has Abstractpub_date
2001-11-05 00:00:00pages
276-84issue
3eissn
0006-3592issn
1097-0290pii
10.1002/bit.1183journal_volume
75pub_type
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