Alcoholic fermentation by immobilised yeast cells

Ethanol production by yeast cells immobilised in carrageenan gel beads and operated in a continuous tubular reactor reached 15 g dm^?3 h^?1 with a glucose feed of 165 g dm^?3; a glucose residence period of 4.6 h was noted. The minimal cell loading to obtain uniform particles was 10⁴ colony-forming units per g of gel, although particles achieved a content of 10⁸ CFU g^?1 independent of the initial cell concentration. Scanning electron and phase contrast microscopy confirmed that growth inside the gel beads was probably limited by substrate diffusion through the denser outer layer observed.