cBSA-147 for the preparation of bacterial biofilms in a microchannel reactor

Whole cells are attractive biocatalysts, particularly if the reaction requires cofactors or involves multiple transformations. Immobilization of the catalyst is often a prerequisite for continuous processes. The highly cationic chemically modified plasma protein bovine serum albumin (cBSA-147) has been applied for the electrostatically mediated immobilization of the planktonic bacterium E. coli BL21 star (DE3), and the resulting biofilms were superior to those formed on poly-L-lysine coated surfaces. The biocatalyst was immobilized in a capillary column (inside diameter of 530 μm and L=30 m) and evaluated in the enantioselective reduction of ethyl acetoacetate to R-(-)ethyl hydroxybutyrate. In continuous operation in the microreactor format, the productivity of the cells was about 30% higher than that determined in a bench-scale fermentation system. This increase is attributed to the improved mass transfer over short geometrical dimensions. The similarity in the results indicates that studies on a biofilm-coated microreactor can be used for the accelerated collection of data for process optimization.