[Influences of internal diffusion on the lipids bio-degradation with immobilized Bacillus sp. cells in fixed bed of...

This paper develops the previous studies on the transfer processes and biochemical reaction kinetics involved in the lipids biodegradation.

The experiments were carried out in 10 1(8 1 working volume) laboratory bioreactor with computer-controlled and recorded Parameters. The basket was placed centered around the stirrer and was filed with Bacillus sp. cells immobilized in alginate. The optimum impellers combination was found to be of two Rushton turbines, the superior one placed outside the basket and the other inside the basket at its inferior extremity.

In the investigated case, the influences of the substrate internal diffusion on physical and biochemical processes have been quantified by means of the Biot number, Thiele modulus and reduction factor lambda. Compared to the system with free bacterial cells, biochemical processes rate is reduced inside the biocatalyst particle for about 150 - 200 times, this effect being more important than in the case of the bioreactor with mobile bed of immobilized yeast cells.

The utilisation of immobilized biocatalysts offers many advantages, but allows the unfolding of the internal diffusion of substrate or product, with negative effect on the overall biochemical process evolution.