HYDRAULIC MODEL OF A GAS LIFT BIOREACTOR WITH FLOCCULATING YEAST

The hydraulic model of a gas lift bioreactor, during a continuous alco holic fermentation by a strongly flocculating strain of Saccharomyces cerevisiae, was studied. Sucrose, at two different concentrations (50 and 100 g/L), was used as substrate and the dillution rate for all the experiments was 1 h(-1). The biomass concentrations were between 85 a nd 110 g dryt weight/L, A stimulus response technique was used, being a pulse of a lactose solution the tracer. Besides, the mixing time was determined by means of the response to a pulse of an acid tracer. The se experiments were carried out using an on-line data-acquisition syst em. The bioreactor behaviour results completely homogeneous, except fo r high substrate and biomass concentrations, being necessary in this c ase to consider a two parameters combined model. Nevertheless, the mea sured of mixing times in the bioreactor have been small enough (betwee n 7 and 14 seconds) with respect to the residence time and the reactio n time of the fermentative process.