Continuous production of honey oligosaccharides in packed-bed reactors with immobilized ?-glucosidase from Metschnikowia reukaufii

The alpha-glucosidase from the yeast Metschnikowia reukaufii, a producer of honey sugars, was immo-bilized on chitosan beads and biomimetic silica nanoparticles under mild and green conditions. Chitosan based derivatives showed apparent activities of about 40-70 U center dot g-1, while silica en-trapped enzyme nanoparticles contained 486 U center dot g-1. Compared to the soluble enzyme, the immo-bilized biocatalysts showed maximum hydrolytic activity at higher temperatures and broader pH interval, in addition to an excellent batch operational stability, maintaining 75-90% of its initial activity after ten subsequent cycles of 20 min reactions. Furthermore, chitosan beads and silica nanoparticles biocatalysts were packed into reactor columns and for the first time employed in the continuous overproduction of isomelezitose and trehalulose. Both systems operated continu-ously for 30 days with excellent isomelezitose yields of about 62 and 54% of the total sugar syn-thesised, respectively. The bioreactor based on chitosan beads had an average productivity of 0.5 kg L-1 per day. This production was increased by almost 10 times (4.9 kg L-1 per day) when a micro-reactor based on the biomimetic silica nanoparticles was used. Consequently, this work constitutes an interesting approach for the production of isomelezitose on an industrial scale, a new high-value functional sugar with interesting applications.