Enzymatic catalysis in organic solvents can enable applications, reactivities, and selectivities that are not accessible in water. The use of enzymes for catalysis in organic solvents has been somewhat hampered by their relatively low-catalytic activity. A new preparation of the enzyme subtilisin Carlsberg (SC) with fumed silica as support (FS) has been developed. This preparation matches and sometimes exceeds the activity of some of the best reported preparations of the same enzyme for use in solvents. The usefulness of our preparation in a packed-bed reactor is explored here. The catalytic characteristics of our preparation containing 5 wt % of enzyme/95 wt % FS in a packed-bed reactor for a model transesterification in hexane is determined. Mass-transfer limitations are explored, and a comparison to batch results is given. The activity of our preparation after prolonged storage as a packed bed is investigated. Our immobilized enzyme preparation may be a step towards more economical enzymatic catalysis in organic solvents. (c) 2006 American Institute of Chemical Engineers.