Optimization Of An Enhanced Ceramic Micro-Filter For Concentrating Escherichia Coli In Water

Recently lower limit of detection (LOD) is necessary for rapid bacteria detection and analysis applications in clinical practices and daily life. A critical pre-conditioning step for these applications is bacterial concentration, especially for low level of pathogens. Sample volume can be largely reduced with an efficient pre-concentration process. Some approaches such as hollow-fiber ultrafiltration and electrokinetic technique have been applied to bacterial concentration. Since none of these methods can provide a concentrating method with a stable recovery rate, bacterial concentration still remains challenging. Ceramic micro-filter can be used to concentrate the bacteria and cross flow system keeps the bacteria in suspension. Similar experiments that used ultrafiltration technique to harvest bacteria showed an average recovery rate of 43% [1] and other studies achieved recovery rates greater than 50% [2]. In this study, an enhanced ceramic micro-filter with 0.14 mu m pore size was proposed and demonstrated to optimize the concentration of E.coli. A high recovery rate (mean value > 90%) and a high volumetric concentration ratio (> 100) were achieved. Known quantities (10(4) to 10(6) CFU/ml) of E.coli cells were spiked to different amounts of phosphate buffered saline (0.1 to 1 L), and then concentrated to a final retentate of 5 ml to 10 ml. An average recovery efficiency of 95.27% with a standard deviation of 5.56% was achieved when the volumetric concentration ratio was 10. No significant recovery rate loss was indicated when the volumetric concentration ratio reached up to 100. The effects of multiple parameters on E.coli recovery rate were also studied. The obtained results indicated that the optimized ceramic microfiltration system can successfully concentrate E.coli cells in water with an average recovery rate of 90.32%.