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The effect of molybdenum on biofilm development
1Microbiology Research Group, Department of Biological Sciences, University College Chester, Parkgate Road, Chester CH1 4BJ, UK.
Abstract:
Little is known about the formation and effects of biofilms on stainless steel pipes in freshwater environments, particularly as they are considered as a direct replacement for copper pipes for 'problem' water. There is some cause for concern especially as stainless steel cannot claim the inherent biocidal potential of copper. As molybdenum is known to be leached out of stainless steel grade 316, in very small amounts, a study was set up to see if molybdenum could retard the development of biofilms. When a comparison of biofilm viable and total cell counts was made between pure molybdenum metal and stainless steel grade 304, it was found that cell counts were significantly higher (P < 0.05) on grade 304 stainless steel after 5 weeks exposure to flowing water (0.64 m s-1). Molybdenum (above a concentration of 1 g L-1) affected the growth rate of Acinetobacter sp, a pioneering bacterium of biofilms in potable water.
Insights
Stainless steel pipes in freshwater may develop biofilms, unlike copper. Molybdenum addition to stainless steel significantly reduced biofilm formation by inhibiting key bacteria growth.
Area of Science:
- Environmental Science
- Microbiology
- Materials Science
Background:
- Stainless steel pipes are considered for freshwater systems, but their biofilm formation differs from copper pipes, which have inherent biocidal properties.
- Concerns exist regarding biofilm development on stainless steel due to the absence of copper's natural antimicrobial effects.
- Molybdenum leaching from grade 316 stainless steel prompted an investigation into its potential to inhibit biofilm growth.
Purpose of the Study:
- To investigate the potential of molybdenum to retard biofilm formation on stainless steel in freshwater environments.
- To compare biofilm development on grade 304 stainless steel versus pure molybdenum metal.
- To assess the impact of molybdenum on the growth rate of pioneering biofilm bacteria.
Main Methods:
- Exposure of grade 304 stainless steel and pure molybdenum metal to flowing freshwater (0.64 m s-1) for 5 weeks.
- Quantification of biofilm viable and total cell counts on both materials.
- Assessment of molybdenum's effect on the growth rate of Acinetobacter sp. at concentrations above 1 g L-1.
Main Results:
- Biofilm cell counts were significantly higher (P < 0.05) on grade 304 stainless steel compared to pure molybdenum metal after 5 weeks.
- Molybdenum, at concentrations exceeding 1 g L-1, demonstrated an inhibitory effect on the growth rate of Acinetobacter sp.
- Acinetobacter sp. was identified as a pioneering bacterium in potable water biofilms.
Conclusions:
- Molybdenum exhibits potential in retarding biofilm development on stainless steel in freshwater systems.
- Grade 304 stainless steel supports significantly higher biofilm formation than pure molybdenum.
- Molybdenum's antimicrobial properties could be leveraged to mitigate biofilm issues in stainless steel piping.
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