Planktonic growth and biofilm formation of Providencia rettgeri under food-related environmental stress conditions and their subsequent resistance to tannic acid treatment.

Providencia rettgeri as an opportunistic foodborne pathogen with a strong biofilm-forming ability under low-nutrition environment gets more and more attention. Tannic acid (TA) has been demonstrated to possess excellent antibacterial property. However, the information regarding the impact of simulated food processing conditions on P. rettgeri planktonic growth and biofilm formation is limited. Using response surface methodology (RSM), the combined effects of temperature (19-37 °C), pH (5-9) and sodium chloride (NaCl) concentration (0.50-2.0 % w/v) were applied to construct planktonic growth and biofilm formation of P. rettgeri . For both RSM models, the increase of NaCl content restricted P. rettgeri growth . The planktonic growth and biofilm formation were maximum with the temperature 27.83°C and 25.41°C. In addition, the results showed that TA remarkably inhibited P. rettgeri under the optimal growth condition at planktonic and biofilm stage. The cell viability of P. rettgeri was decreased by TA, which was confirmed by destroying cell membrane and producing endogenous reactive oxygen species (ROS). Moreover, TA significantly inactivated P. rettgeri biofilm, as verified by biofilm elimination and morphology observation. The obtained models in this study may be useful tools to describe the impact of temperature, pH, and NaCl concentration applied during food processing on the growth by P. rettgeri , which expanded the understanding of the impacts of food-related conditions on planktonic growth and biofilm formation . This work demonstrates the pattern and removal of P. rettgeri planktonic growth and biofilm formation, providing a potential framework for foodborne pathogens and removal strategy.