Formation of microbial biofilms on stainless steel with different surface roughness

Yana Yevchuk,Igor Stadnyk,Ganna Sabadosh,Tetiana Hushtan

doi:10.5219/1190

Abstract

The physical essence of the formation and influence of bacteria on the surface of technological equipment in the dairy industry is considered as an essential factor leading to contamination of dairy products and is a major hygienic problem. The ability of microorganisms on the surfaces of technological equipment to form biofilm forms and requirements for steel grade, relief, and its roughness were analysed. The effect of surface roughness on promoting or preventing adhesion and reproduction of biofilm forms of bacteria, which reduce the efficiency of sanitary processing of dairy equipment and thereby increase the microbial contamination of dairy products with shortened shelf life, is substantiated. Research about the process of bacterial adhesion to the surface of metals with different roughness depending on the size and shape is presented. It is found that on the surface of stainless steel with roughness 2.687 ±0.014 micron film formation process in Escherichia coli and Staphylococcus aureus are similar from 3 to 24 hours and does not depend on the size of the bacteria, and accordingly allows us to argue that rod-shaped and coccid bacteria attach freely in the hollows of the roughness are the beginning of the process of the first stage of biofilm formation. It is found that on the surface of stainless steel with roughness 0.95 ±0.092 micron film formation process in S. aureus is more intense than in E. coli. Thus, within 3 hours of incubation, the density of biofilms formed S. aureus was 1.2 times bigger than biofilms E. coli, by the next 15 hours of incubation formed biofilms S. aureus were, on average, 1.3 times denser. It is established that S. aureus due to its spherical shape is able to fit in the hollows of the roughness 0.95 ±0.092 μm and faster to adhere to the surface at the same time. E. coli, due to its rod-like shape, with such surface roughness, can adhere to the cavities only over its entire length. It is proved that by surface roughness 0.63 ±0.087 μm film intensity S. aureus was, on average, 1.4 times faster than E. coli, for roughness 0.16 ±0.018 micron film formation process took place equally for S. aureus and E. coli, but biofilms were lower in density than those formed on roughness 0.63 ±0.087 micron. Studies suggest that the use of equipment in the dairy industry with a roughness of less than 0.5 microns will reduce the attachment of microorganisms to the surface and reduce the contamination of dairy products.

Highlights

With the widespread introduction into food production of modern automated, complex mechanized lines, when the processing speed of non-Newtonian food masses has increased significantly and new structural materials are widely introduced, there is always a need to study the adhesion strength and its effect on the passage of processes
We have found that apart from surface roughness the biofilm formation is influenced by the form and size of microorganism cells
At a roughness of 0.16 ±0.018 μm, the film-forming process proceeded for S. aureus and E. coli, but the formed biofilms were lower in density than those formed at a roughness of 0.63 ±0.087 μm

Summary

Introduction

With the widespread introduction into food production of modern automated, complex mechanized lines, when the processing speed of non-Newtonian food masses has increased significantly and new structural materials are widely introduced, there is always a need to study the adhesion strength and its effect on the passage of processes. Compliance with technological processes is directed to the separation zone taking into account both the type and condition of the surface of technological equipment and the structural and mechanical properties of the food masses. The main factor that reduces the shelf life and safety of food are microorganisms (Kukhtyn et al, 2017; Shaheen et al, 2010; Verran et al, 2010). Among the many factors that influence the adhesion process are researchers (Whitehead and Verran, 2007) consider that surface properties play a major role. The presence of bacteria on the surfaces of technological equipment in the dairy industry is considered as an important factor that can lead to contamination of dairy products and is considered as an important hygienic

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