Bacterial growth and biofilm formation of Escherichia coli and Enterococcus faecalis on glass, polystyrene, and AISI 304L stainless steel.

Abstract

Biofilm formation on stainless steel surfaces represents a challenge for microbiological control in dairy facilities and the food industry. This study aims to evaluate the formation of Escherichia coli and Enterococcus faecalis biofilms under different conditions on glass, polystyrene, and AISI 304L stainless steel. Growth curves were used to determine specific growth rates of 1.2 h^-1 and 1.4 h^-1, and generation times of 34 and 30 min for E. coli and E. faecalis, respectively. Subsequently, the ability of both species to form biofilms in the presence of different glucose concentrations was evaluated both qualitatively and quantitatively. Both bacteria developed biofilms on the three tested surfaces, and in all cases, glucose supplementation promoted biofilm formation. E. coli showed a greater dependence on glucose concentration, whereas E. faecalis exhibited more stable biofilm formation once the medium was supplemented. Based on these results, the experimental conditions for the reproducible formation of biofilms on glass, polystyrene, and AISI 304L stainless steel were established, defining incubation at 28 °C in Luria-Bertani (LB) medium supplemented with 0.75% glucose for 48 h as the optimal conditions. This experimental model provides the foundation for the next stage, which aims to evaluate the effect of Plasma Activated Water (PAW) as an innovative strategy for controlling bacterial biofilms on stainless steel surfaces of relevance to the food industry.