Hollow Fiber Microfiltration of Microorganisms from Food and Water

This presentation discusses the factors involved in designing and operating an automated hollow fiber microfiltration system for concentrating microorganisms from complex fluids that can rapidly foul membranes.

By combining pretreatment of the fluids prior to microfiltration, with an automatically controlled, cross-flow microfiltration system where flow occurs on both retentate and permeate sides of 0.3mm diameter hollow fiber membranes, the cells are concentrated by a factor of 500 to 1000 in 2 hours or less. Principles and approaches for controlling fouling, together with explanation of the attendant microfluidic phenomena, are discussed.

The concentration of cells from food derived samples that utilizes hollow fibers in an integrated microfluidic system provides a window on future technology for rapid pathogen detection. The lessons learned have led to prototype systems (refer to picture) that are currently being validated for automated detection of pathogens in liquid samples extracted from foods including ground meat, chicken carcass, and vegetables, as well as from surface water.

Microfiltration removes a large volume of fluid from an extract containing a small number of microorganisms and decreases the 50 to 10 L volume of fluid to a 1 mL or less in 2 hrs. When followed by centrifugation, a concentrate of living microorganisms in 50 to 500 microliters is obtained. This small volume contains sufficient numbers of bacterial cells so that they may be effectively probed for presence of pathogens on a “first alert” basis. A positive result signals the need for further investigation.