Immobilization of yeast cells with cross-linked chitosan beads

Abstract

Ethanol-producing yeast cells were entrapped with cross-linked chitosan beads (CCB). In repeated batch culture, the number of yeast cells immobilized with CCB finally reached 1.2 × 1010 cells/ml-beads. While this result was almost the same as with calcium alginate, the ethanol concentration produced with CCB was about 1.5 times higher than that with calcium alginate. The most suitable CCB pore size to immobilize yeast cells was about 10 μm, while to produce ethanol it was approximately 15 μm. CCB modified chemically with the trimethylammonium group had a high capacity to immobilize yeast cells, but the ethanol concentration produced was almost the same as with unmodified CCB. CCB as a carrier had higher yeast cell immobilizing and ethanol production capacities than the commercial carriers SIRAN and FIBERM. In continuous culture, ethanol was produced for thirty days at least at an average concentration of 51 g/l when the dilution rate was 0.1 h−1.