drug delivery systems for reducing the quantity of residual antibiotics reaching the colon following oral or parenteral antibiotic therapy , and for delivering metallo - dependent enzymes , and methods of use thereof , are disclosed . the drug delivery systems include pectin beads that encapsulate the active agent . the pectin is crosslinked with zinc or other divalent cations , and the pectin beads are coated with eudragit ®- type polymers . the delivery of the active agent can be modulated to occur at various pre - selected sites of delivery within the intestinal tract . a stable metallo - dependent enzyme formulation can be delivered to the lower intestine or colon . the use of zinc cations to crosslink the pectin is particularly preferred when the metallo - dependent enzymes are zinc dependent , where other cationic used to gel the pectin beads might adversely affect the activity of such metallo - dependent enzymes .