COIMMOBILIZATION OF YARROWIA-LIPOLYTICA CELLS AND INVERTASE IN POLYELECTROLYTE COMPLEX MICROCAPSULES

Invertase and Yarrowia lipolytica cells were coimmobilized in polyelec trolyte complex (PEG) microcapsules prepared from sodium cellulose sul fate and poly(dimethyldiallylammonium chloride). With these studies on coimmobilization of enzymes and viable cells, the question of supplyi ng the substrate from a nonmetabolizable substance was addressed. It w as shown to be favorable to immobilize the enzyme prior to encapsulati on onto an insoluble carrier material in order to avoid leakage of the enzyme from the capsules. Small particles of poly(aminomethyl styrene ) were used to immobilize the enzyme successfully by covalent binding via glutaraldehyde. After preimmobilization and encapsulation of polys tyrene-bound invertase, 17% of the initial activity was retained. The growth and product formation profiles of the microorganisms were chang ed by coimmobilization of the invertase-polystyrene complex, and the c apsule stability and cell-retaining ability of the PEC capsules were s ignificantly increased as a result of supplying the carbon source in t he capsule interior. The coimmobilized cell/enzyme-carrier complex was subjected to 800-1000 h of continuous fermentation. The productivity, however, was considerably lower than that of Y. lipolytica cells enca psulated alone, without invertase. The mean production rate of citric acid by the coimmobilized enzyme/cell system was 0.014 g citric acid l (-1) h(-1) in comparison to 0.125 and 0.25 g l(-1) h(-1) by the encaps ulated and free cells, respectively.