Immobilization of Saccharomyces uvarum cells in porous beads of polyacrylamide gel for ethanolic fermentation

A procedure which does not involve the use of an immiscible organic solvent phase is described for the entrapment of yeast cells in porous beads of polyacrylamide gel. The cells are rapidly dispersed at 4 degree C in an aqueous solution containing sodium alginate and acrylamide-N,N'-methylene-bis-acrylamide monomer, and the suspension is immediately dropped into a solution of calcium formate to give calcium alginate coated beads. Polyacrylamide gel forms within the bead. The calcium alginate is subsequently leached out of the composite bead with either sodium citrate or potassium phosphate buffer solution. Cells of Saccharomyces uvarum ATCC 26,602 entrapped in such polyacrylamide beads ferment cane molasses in batch mode at higher specific ethanol productivity than a free cell suspension. Their volumetric productivity in continuous fermentation is higher than that of Ca super(2+)-alginate immobilized cells.