Continuous Ethanol Production Through Fermentation with Glucose and Xylose by Immobilized Yeasts in Two Cascade Fixed Beds

Glucose and xylose were used as mixed carbon sources for ethanol production by a cascade immobi-lized-cell reactor.In the first fixed-bed reactor,immobilized S.cerevisiae was used to metabolize the glucoseanaerobically,and in the second fixed-bed column,the immobilized Pichia stipitis was applied to metabolize xy-lose aerobically.The effect of xylose on the glucose uptake by S.cerevisiae and the effect of ethanol on the xylosemetabolization by P.stipitis were studied.A mathematical model taking both tbe substrate and xylose inhibitioninto consideration was suggested for the description of the two-substrate fermentation process,and a total effec-tiveness factor ηin the model was derived to take into account the mass transfer resistances of intra-particlesand liquid films.Calculated results are in fair agreement with the experimental data.