Entrapment of microbial cells within polyurethane hydrogel beads with the advantage of low toxicity

Summary A new method is described for the entrapment of microbial cells in polyurethane (PUR) hydrogel beads. This hydrogel is produced from a hydrophilic pre-polymer blocked with bisulphite by adjusting the pH between 4 and 6.5. Bisulphite-blocked isocyanate has a substantially lower toxicity against living cells than unblocked (conventional) isocyanates. The poly(carbamoylsulfonate) (PCS) hydrogels have optimal elastic properties and therefore can be used for a matrix of biocatalysts in an agitated reactor as well as in a fluid-bed reactor. The results of ethanol fermentation ofSaccharomyces cerevisiae entrapped in PCS hydrogel beads, and of the denitrification activity of immobilizedParacoccus denitrificans are promising. In contrast, entrapped cells in conventional PUR hydrogels didn’t show any activity.