Production of cytidine 5´-monophospho-N-acetyl-(beta)-D-neuraminic acid (CMP-sialic acid) using enzymes or whole cells entrapped in calcium pectate–silica-gel beads

The present study focuses on the application of immobilization technology to enzymic sugar syntheses. The paper describes an improved silica–alginate matrix established for entrapment and encapsulation. The replacement of alginate with pectate provided enhanced chemical resistance of the matrix, which allows the use of 1% (w/v) polyphosphate in reaction mixtures. Polylysine, a reagent for silica condensation, was replaced by a much cheaper alternative, namely polyethyleneimine. The proposed design was applied in the production of cytidine 5´-monophospho-N-acetyl-(beta)-D-neuraminic acid (CMP-sialic acid) by immobilized recombinant enzymes or Escherichia coli cells containing overexpressed enzymes. A comparison between these two strategies was made. On the basis of the results we conceptualized a system to synthesize sialyloligosaccharides by using a biocatalyst entrapped in calcium pectate–silica gel beads.