Reactors for ethanol production using immobilised yeast cells

Ethanol production by immobilised yeast cells in packed-bed column reactors was significantly affected by the hold-up of CO₂ produced during the fermentation. Compartmentalisation of the reactor minimises CO₂ hold-up and prevents flotation of immobilised cell beads during operation and bead rupture during shut-down conditions. In a reactor of dimensions 2·2 × 60 cm, a rate of ethanol production of 5·11 g h^?1 at a dilution rate of 1·27 h^?1 was achieved, when 18% (w/v) glucose solution was fed at the bottom at pH 5·5 and temperature 33–35°C. In larger reactors of sizes 4 ×; 40 cm and 8 × 80 cm the rates of ethanol production and CO₂ hold-ups were 5·11 and 5·37 g h^?1 and 48·66% and 40·66% and 40·79% of the void volume at dilution rates of 1·27 h^?1 and 1·67 h¹, respectively. The CO₂ hold-ups in column reactors (4 × 40 cm) held in inclined (43° from horizontal) or horizontal positions were 41·33% and 46·67% of the void volume, respectively. Double and triple series reactors (each of dimensions 2·2 × 60 cm) showed better performance than a single verticle reactor (2·2 × 60 cm).