A method is described for constructing a simple laboratory-scale nonwoven filament biocatalytic filter (FBF) from multilayer acrylic vinyl acetate copolymer coated thread (yarn) potentially useful for investigation of biotransformations using entrapped enzymes or viable microorganisms. The porous structure of a commercial 128 mu m, 279 denier, 100% polyester thread was sealed with a latex coat (precoat), then coated with a latex + sulfanilamide-azocasein mixture, and finally coated with a latex top coat to generate the multilayer coated thread. The FBF was constructed by drawing the thread across a 4 cm diameter rubber O-ring in the form of multiple layers and sealing the layers with silicone sealer. The FBF is combatible with a commercially available filter housing containing a flow distributor. A method for characterizing the permeability of the sealant (top) coat of the FBF using azocasein release was also developed.