PRODUCTION OF CITRIC-ACID WITH IMMOBILIZED YARROWIA-LIPOLYTICA

Citric acid was produced with immobilized Yarrowia lipolytica yeast in repeated batch-shake-flask and air-lift fermentations. In active and passive immobilization methods calcium alginate, kappa-carrageenan, polyurethane gel, nylon web and polyurethane foams were tested as carriers in repeated-batch fermentations. The highest citric acid productivity of 155 mg l-1 h-1 was reached with alginate-bead-immobilized cells in the first batch. A decrease in bead diameter from 56 mm to 2-3 mm increased the volumetric citric acid productivity threefold. In an air-lift bioreactor the highest citric acid productivity of 120 mg l-1 h-1 with a product concentration of 16.4 g l-1 was obtained with cells immobilized in kappa-carrageenan beads.