Biofilm formation by Bacillus subtilis: Effect of Oxide Layers and Surface Roughness

Sammanfattning

Biofilms in the dairy and food industry, particularly those formed by Bacillus subtilis, present significant contamination and food safety challenges. This thesis investigates the impact of stainless steel surface properties, specifically oxide layer formation and surface roughness of polished coupons, on biofilm development. Bacillus subtilis SA 22 (NCA 72-52; DSM 4181) was cultivated using a CDC Biofilm Reactor® (BioSurface Technologies Corporation), with stainless steel coupons subjected to various treatments, including citric acid passivation, polishing, and chemical cleaning. Surface wettability was assessed through contact angle measurements, while biofilm growth was quantified using relative fluorescence units (RFU) and UV microscopy. Although surface treatments affected hydrophilicity, they did not significantly reduce biofilm formation. These results indicate that effective biofilm prevention in food processing environments requires more comprehensive strategies beyond surface modification. This study enhances understanding of microbial adhesion mechanisms and provides insights relevant to the design of safer food processing systems.