Modeling the process of microbial biofilm formation on stainless steel with a different surface roughness

Abstract

This paper reports a study into the process of bacteria adhesion to surfaces of different roughness depending on sizes and shapes. It was determined that at the surface of stainless steel with a roughness of 2.687±0.014 µm, the film formation process in E. coli and S. aureus occurred equally over 3 to 24 hours and did not depend on the size of bacteria. This makes it possible to argue that rod-shaped and coccal bacteria freely attach themselves in the grooves of roughness, followed by the initial process related to the first stage of a biofilm formation. During sanitization, the hollows of roughness could host both the coccal and rod-shaped bacteria. At the surface of steel with a roughness of 0.95±0.092 μm the process of film formation in S. aureus occurred more intensely than in E. coli. Within 3 h of incubation, density of the formed biofilms S. aureus was 1.2 times larger compared to the biofilms E. coli. Over the following 15 hours of incubation, the biofilms S. aureus were on average 1.3 times denser. This suggests that S. aureus, due to a spherical form, can stay put in the hollows of roughness of 0.95±0.092 µm and quicker attach to the surface. At the same time, E. coli, owing to a rod-shaped shape, would attach at such a surface roughness to the hollows lengthwise only. It has been proven that at a surface roughness of 0.63±0.087 µm the intensity of the S. aureus film formation was on average 1.4 times faster than in E. coli. However, at a roughness of 0.16±0.018 μm the process of film formation occurred equally in E. coli and S. aureus, but the biofilms demonstrated lower density compared to those that formed at a roughness of 0.63±0.087 µm. Thus, the use of equipment with a roughness of less than 0.5 µm in the dairy industry will make it possible to reduce the attachment of microorganisms to surface and to decrease contamination of dairy products