Synthesis of lipase-catalyzed saccharide-fatty acid esters using a packed bed bioreactor system with continuous re-circulation of reaction medium a continuation of batch-mode-related research /

by Obiri, Oriana Okutu.

The purpose of this thesis study was to further study the batch synthesis of lipasecatalyzed saccharide-fatty acid esters and to introduce the fed-batch synthesis of saccharide-fatty acid esters as a preliminary design to the continuous synthesis of these esters in a packed bed bioreactor system. The batch reaction method is the conventional mode of synthesizing saccharide-fatty acid esters on a lab-scale basis and some conversion-related parameters of the reaction mode were investigated. These experiments included investigating the effect of water content on the equilibrium conversion of fructose oleates and exploring the activity retention of immobilized Rhizomucor miehei lipase (RML) in successive batch reactions. The batch synthesis of other saccharide-oleic acid esters was also a point of interest and was studied. Results from the batch-related experiments revealed the following results: that the there is no loss of activity after successive use of the immobilized RML in batch reactions, that the presence of water reduces the thermodynamic equilibrium-controlled conversion of the reaction, and that the product conversion and the reaction rate of each type of saccharide are different. Motivated by drawbacks associated with the batch mode of esterification, the fedbatch synthesis mode was proposed as a preliminary design towards the continuous synthesis mode, and was applied to the lipase-catalyzed esterification reaction between fructose and oleic acid in the lab. The study was approached by first designing and building a packed bed bioreactor system. Lipase-catalyzed synthesis of saccharide-fatty iv acid esters was then conducted by continuous re-circulation of the reaction medium through the packed-bed reactor. Success was achieved in designing and assembling the bioreactor system and it was employed for the fed-batch synthesis of saccharide-fatty acid esters. The results obtained demonstrated that the synthesis of saccharide-fatty acid esters in a packed bed bioreactor with continuous re-circulation of reaction medium did achieve a high product conversion without disadvantages such as the need for lipase recovery and replacement, large requirement for labor and frequent shutdown and start-up procedures. A kinetic mathematical model was created to predict the mass fraction of monoesters that were present in the re-circulation stream and that produced in the packed bed reactor. It was observed from the results that the derived kinetic model was reliable and correlated well with the experimental data. v