CITRIC-ACID PRODUCTION IN A BUBBLE-COLUMN REACTOR USING CELLS OF THE YEAST CANDIDA-GUILLIERMONDII IMMOBILIZED BY ADSORPTION ONTO SAWDUST

Cells of the yeast Candida guilliermondii have been immobilized by ads orption onto sawdust and used in a bubble-column reactor for the conti nuous production of citric acid. At a dilution rate of 0.21 h(-1) in a nitrogen-limited medium containing glucose, a reactor productivity of 0.24 g l(-1) h(-1) has been achieved which is twice that observed in a batch fermenter culture using freely suspended cells. The correspond ing specific production rate was 0.024 g citrate g(-1) biomass h(-1) w hile the yield was 0.1 g citrate g(-1) glucose utilized These latter v alues were lower than those observed using freely suspended cells, ind icating that further improvements can be made to the operation of the reactor. In comparison with literature reports describing other cell i mmobilization techniques, adsorption onto sawdust allows similar react or productivities while being cheap and permitting simple immobilizati on and reactor operation.