Encapsulation in LentiKats of dextransucrase from Leuconostoc mesenteroides NRRL B-1299, and its effect on product selectivity

Insoluble (cell-bound) dextransucrase from Leuconostoc mesenteroides B-1299 was encapsulated in highly elastic and stable hydrogels formed by polyvinyl alcohol. The gelation was carried out by controlled partial drying at room temperature, resulting in lens-shaped particles, called LentiKats. A similar recovery of activity (approximately 55%) was achieved when compared with entrapment in calcium alginate gels. Under reaction conditions, the protein leakage in LentiKats was reduced from 18% to 4% by pre-treatment of the dextransucrase with glutaraldehyde. The immobilized dextransucrases were tested in the acceptor reaction with methyl alpha-D-glucopyranoside. The conversion to oligosaccharides using Lentikat-dextransucrase was higher than that obtained for alginate-dextransucrase, probably due to the reduction of diffusional limitations derived from its lenticular shape. In addition, a shift of selectivity towards the synthesis of oligosaccharides containing alpha(1-->2) bonds was observed for the Lentikat-biocatalysts. These non-digestible compounds are supposed to be specifically fermented by beneficial species of the human microflora (prebiotic effect ) . The Lentikat-entrapped dextransucrase can be efficiently reused in this process at least for five cycles of 24 h.