PDMS Flow Cell for Monitoring Bacterial Adhesion Capacity of Escherichia coli O157:H7 in Beverages

Aims: To develop and standardize a polydimethylsiloxane (PDMS) flow cells for monitoring bacterial adhesion capacity of biofilm formation by Escherichia coli O157:H7 in Beverages industry.

Study Design: PDMS chip was fabricated in house and placed in a metal chamber. The bio-Ferrograph generated different flow rates of bacterial cell suspension in the PDMS cells.

Methodology: PDMS flow cells were used to monitor bacteria adhesion capacity of E. coli O157:H7 inoculated into some beverages. The Effect of fluid flow rate and temperature on bacteria adhesion capacity was studied in order to standardize the system. Buffer system of adhesion was modified by varying the concentrations of PBS, Saline concentrations and PH value. The impact of elapsing time and initial number of bacterial cells were investigated. Fluorescence imaging of biofilm formation was also captured.

Results: Bacterial adhesion capacity reached the maximum at 0.1 ml/min and then dramatically dropped down when fluid flow rate increases. Maximized adhesion capacity occurred with a buffer system of 0.01M Phosphate buffer, 1.0% NaCl, pH 7.5 at 30°C. A complete linear relationship (R2; 0.9956 - 0.9815) occurred between adhesion capacity of E. coli O157:H7 cells and elapsing time of food beverage. This linear relationship would help to predict and study biofilm formation in fluid and beverage industry. Maximum adhesion capacity occurred with beverages at the following order: skim milk followed by apple juice and then grape juice.

Conclusion: PDMS flow cell enables non-destructive, in situ investigation of bacteria adhesion capacity as an initial step for biofilm formation in real time under a wide range of flow rates, nutrient conditions, fluid temperature, and elapsing times. It is inexpensive, simple, disposable, easy-to-use, and can accurately mimic the dynamic flow conditions in beverage industry.