The use of chitosan to increase the stability of calcium alginate beads with entrapped yeast cells.

A method was developed for increasing the stability of calcium alginate beads with entrapped Saccharomyces cerevisiae cells. Polyelectrolyte complexes were used as surface-coating materials by dropping alginate into chitosan. The coacervation agent sodium triphosphate was needed for the formation of the polyelectrolyte complexes. Gel beads maintained their rigidity during ethanol production and were chemically stable in phosphate buffer. No differences in ethanol production were found between S. cerevisiae immobilized in calcium alginate and in calcium alginate coated with polyelectrolyte complexes. The maximum productivity by immobilized S. cerevisiae cells was 74.1 g of ethanol/h per g of gel beads obtained at pH 4.8-6.0 and at 30 degrees C.