The impact of material properties, nutrient load and shear stress on biofouling in food industries

Abstract

Abstract:In the food industry, biofilm formation in pipes, equipment and cooling systems increases maintenance costs, decreases operational efficiencies and is a source of contamination.Shear stress, nutrient load and surface material are important variables affecting the biofilm onset in industry. In this work, the combined impacts of these variables were assessed using three different materials (glass, copper and stainless steel), two nutrient loads (high and low nutrient medium) and two hydrodynamic conditions (static and dynamic). Initial adhesion and biofilm formation were studied in microplates usingEscherichia coli as a model organism.Surface material was the factor with the strongest impact and adhesion/biofilm formation were correlated with surface hydrophobicity. However, the impact of this variable was dependent on the nutrient load and imposed shear stress. It was also found that, for the majority of the situations tested, initial attachment performance is a good predictor of biofilm formation behaviour and that the effects observed during attachment are amplified during biofilm maturation. Since shear stress is a major determinant in cell adhesion, the results of this study may find application in industrial systems operating at flow rates between 0.001 and 600 m 3 h -1 depending on tube material and diameter.

Biofilm formation behaviour of marine filamentous cyanobacterial strains in controlled hydrodynamic conditions

“…Since the contact angle of water on glass was θ w = 48.55 ± 2.41 and in perspex θ w = 73.05 ± 3.42, perspex is relatively hydrophobic compared to glass, exhibiting a lower wettability. Although lower values for glass have been reported, some studies performed with glass surfaces, also showed values in the 40° range (Sener et al ., ; Thukkaram et al ., ; Gomes et al ., ; Moreira et al ., ). This slightly increased value may be related to the composition of this specific glass although other glass surfaces that can be used to construct submerged devices (underwater cameras, measuring devices or sensors) can have different hydrophobicities.…”

“…Amongst the parameters that affect biofilm development, physicochemical factors related with the surface (Crawford et al ., ) and flow velocity and shear rate (Allen et al ., ) are some of the most important. There is evidence that shear forces affect not only biofilm structure but also composition, mass transfer, exopolysaccharides production, energy metabolism and can also induce genetic or molecular changes in biofilms (Moreira et al ., ). It has been reported that a slow flow of water (0.2 m·s −1 ) promotes the growth of filamentous green algae and cyanobacteria (Minchin and Gollasch, ; Flemming et al ., ) and that biofouling can be favoured at low fluid velocities.…”

Surface conditioning with <em>Escherichia coli</em> cell wall components can reduce biofilm formation by decreasing initial adhesion

“…Unconditioned polystyrene coupons were used as control. After 30 min of bacterial adhesion and 24 h of biofilm formation, the coupons were retrieved from the PPFC and total bacterial counts were obtained by direct staining with 4′,6-diamidino-2-phenylindole (DAPI; Sigma-Aldrich, Portugal) [38]. Cells were visualized under an epifluorescence microscope (Eclipse LV100; Nikon, Japan) equipped with a filter block sensitive to DAPI fluorescence (359-nm excitation filter in combination with a 461-nm emission filter).…”

Effect of surface conditioning with cellular extracts on Escherichia coli adhesion and initial biofilm formation

“…Unconditioned polystyrene coupons were used as control. After 24 h, coupons were removed from the PPFC and total bacterial counts were obtained by direct staining with 4',6diamidino-2-phenylindole (DAPI) (Moreira et al, 2015a). Cells were visualized under an epifluorescence microscope (Eclipse LV100; Nikon, Japan) equipped with a filter block sensitive to DAPI fluorescence (359-nm excitation filter in combination with a 461-nm emission filter).…”