OXYGEN DIFFUSIVITY IN CALCIUM ALGINATE GEL BEADS CONTAINING GLUCONOBACTER SUBOXYDANS

Gaining insight into the mass transfer characteristics in immobilized enzyme and microorganism systems bears much importance because of thei r widely increased use in industrial scale production as well as for a nalysis purposes. In this study, the effective diffusion coefficient o f oxygen in calcium alginate gel with and without cells has been deter mined by the Moment Analysis Method for the first time in literature. When the gel concentration was increased from 1 to 3%, D-e values of o xygen varied between 2.54 x 10(-5) cm(2)/s and 2.58 x 10(-5) cm(2)/s i ndicating almost no dependency on gel concentration. However, a decrea se in effective diffusion coefficient (from 2.55 cm(2)/s to 2.47 cm(2) /s) was observed with increased immobilized Gluconobacter suboxydans c oncentration in the range of 0 to 6%. Experimental results on liquid-p article mass transfer coefficient revealed a negligible external mass transfer resistance. Effectiveness factor for the bioreactor system wa s also calculated and found to be 0.39 and 0.21 for gel beads of 0.1 a nd 0.2 cm radius respectively. It is concluded therefore that the use of smaller gel beads could substantially improve the production effici ency in similar bioreactors.