Predictive modeling for hot water inactivation of planktonic and biofilm-associated Sphingomonas parapaucimobilis to support hot water sanitization programs

Abstract

Hot water sanitization is a common means to maintain microbial control in process equipment for industries where microorganisms can degrade product or cause safety issues. This study compared the hot water inactivation kinetics of planktonic and biofilm-associated Sphingomonas parapaucimobilis at temperatures relevant to sanitization processes used in the pharmaceutical industry, viz. 65, 70, 75, and 80°C. Biofilms exhibited greater resistance to hot water than the planktonic cells. Both linear and nonlinear statistical models were developed to predict the log reduction as a function of temperature and time. Nonlinear Michaelis–Menten modeling provided the best fit for the inactivation data. Using the model, predictions were calculated to determine the times at which specific log reductions are achieved. While ≥80°C is the most commonly cited temperature for hot water sanitization, the predictive modeling suggests that temperatures ≥75°C are also effective at inactivating planktonic and biofilm bacteria in timeframes appropriate for the pharmaceutical industry.

Keywords:

• Biofilm
• planktonic
• sanitization
• hot water
• inactivation

Acknowledgements

The authors acknowledge the technical support of Denise Pride (Sterility Assurance, Baxter Healthcare Corp.), microbiologists Lindsey Lorenz and Kelli Buckingham-Meyer, and interns Blaine Fritz and Danielle Goveia of the Standardized Biofilm Methods Laboratory at the Center for Biofilm Engineering (Montana State University).

Notes

1. The planktonic and sessile bacteria were grown at different temperatures because optimization studies (unpublished data) indicated that these conditions produced robust microbial challenges for hot water treatment.