Cell Encapsulation Technology: the Effect of Nonionic Surfactants on the Diffusional Properties of Hydrogel Capsules

Improved fermentation processes using immobilized systems for the synthesis of vitamin compounds are gaining importance because their recovery and purification from suspended systems remains highly complex. Problems with mass transfer are common in immobilized systems. One of the most important factors that affects mass transfer, other than capsule size, is the pore size of the gel membrane. The main objectives of this study are to investigate the effect of nonionic surfactants on the diffusion properties of capsules then compare fermentation efficiencies in suspended vs. attached growth systems. Results from this work showed that the addition of surfactants that are more water soluble during capsule preparation increased the diffusion coefficient of riboflavin away from capsules while the addition of surfactants that are more oil soluble increased the diffusion coefficient of glucose into the capsules. In addition, all three reactors using cells immobilized in capsules exhibited better operational stability and less fluctuation at higher dilution rates. This suggests that capsules made with the addition of nonionic surfactants exhibit superior performance in continuous systems at higher dilution rates. These results show great promise for the continuous immobilized cell reactor for riboflavin production using capsules made with nonionic surfactants.