Innovative Laboratory Technique for Testing of Bacterial Filtration Efficiency of Nanofiber-based Filters

The air filters with high Bacterial Filtration Efficiency (BFE) should help protect people effectively against various air borne particles including bacteria. In general, antibacterial properties of nanofiber membranes are tested by the conventional agar diffusion test where the small piece of test specimen is placed on agar plate and inoculated with test microorganism and incubated. This method provides only a qualitative impression of how effective the antibacterial additive is against the bacteria. From this viewpoint, agar diffusion test is not sufficient for characterizing filtration properties such as how much protection the filter would provide against the bacteria dispersed in air. This paper describes a new laboratory technique for testing BFE of nanofiber membrane based filters that provides quantitative results. Nano-fiber based materials were prepared by electro-spinning process and tested using this new technique. A bacterial aerosol was prepared using non-pathogenic E.coli. Both protein based nanofiber filters and commercial air filter were tested. It was found out that BFE of the filter material covered by protein based nanofibers was 100% whereas the commercial filter BFE was low at about 21%.