Abstract #W156

# W156
Effects of surface modification on bacterial and spore adhesion in dairy handling materials.
Garrett T. Walsh*1, Rafael Jimenez-Flores1, 1California Polytechnic State University, San Luis Obispo, CA.

The objective of this work was to demonstrate how stainless steel microstructure, material processing and surface treatment affect the attachment of spores, and the subsequent development of biofilms on the surface of AISI 316L Stainless steel, the typical milk handling and processing material. Stainless steel coupons with different surface finishes were prepared (as received, 220 grit, 400 grit and 800 grit) and characterized by contact profilometry and scanning electron microscopy. In addition, autogenously welded samples were produced for each surface roughness. Samples were exposed to both sterile and bioactive solutions for 5 and 20 h periods. Corrosion resistance was subsequently measured using cyclic polarization testing in each surface and solution pairing. Samples were examined using scanning electron microscopy and epifluorescence microscopy. The former was used to characterize surface damage, identify film presence, and examine spore attachments. The latter was used to quantify attachment of Bacillus licheniformis and to estimate the thickness of biofilms formed. The work has demonstrated that surface preparation had a significant effect on attachment and proliferation (P < 0.05). Furthermore welding had a significant effect on attachment and electrochemical reactivity (P < 0.05). The electrochemical reactivity of the material as measured by stable pitting potential and measured passive current is also affected by both surface roughness and by bioactivity of the solution. Metastable pitting is common in all solutions, stable pitting potential is lower in bioactive solutions and the passivation current is greater in bioactive solutions. Microstructure of the material is critical to its behavior, as is the complexity of the solution. Planktonic populations are not a direct indication of the sessile populations.