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Microbial growth and accumulation in industrial metal-working fluids
I Mattsby-Baltzer1, M Sandin, B Ahlström
1Department of Clinical Bacteriology, University of Göteborg, Sweden.
Abstract:
The dynamics of microbial growth in metal-working fluids (MWF) and the effect of the addition of biocides were studied in large fluid systems, in this case, one central tank which holds 150 m3. In this system, populations of Pseudomonas pseudoalcaligenes (greater than 10(8) CFU/ml) were sustained for a year, although large quantities of biocides were added. Quantitation of 3-OH lauric acid, a marker for many Pseudomonas spp., by gas chromatography indicated that the bacterial biomass exceeded the viable counts by approximately 15 times. Fungi were grown on several occasions, the dominating genera being Fusarium and Candida. Soon after the old MWF was removed and the tank was provided with fresh MWF, which consisted of an emulsion of mineral oil in water, there was a massive growth of P. pseudoalcaligenes that reached levels of greater than 10(8) bacteria per ml. Initially, only low concentrations of other species were found for some weeks. After this period, different enterobacteria and other gram-negative rods often appeared at high concentrations (10(7) and 10(8) bacteria per ml, respectively). Bacteria identified as P. pseudoalcaligenes showed great variation with respect to colony morphology and a certain heterogeneity with respect to biochemical characteristics. Certain bacterial species grew as microcolonies on metal strips immersed in the circulating MWF, but P. pseudoalcaligenes was not recovered from this habitat. The total bacterial count in the air surrounding the machines in the metal-working shop showed an inverse relation to increasing distance from the machine. The concentration of bacteria in the air varied because of the number of machines in use, temperature, and humidity.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Microbial growth, particularly Pseudomonas pseudoalcaligenes, persisted in large metal-working fluid (MWF) systems despite biocide use. Bacterial biomass significantly exceeded viable counts, indicating challenges in controlling microbial populations in MWF.
Area of Science:
- Industrial Microbiology
- Environmental Science
- Biotechnology
Background:
- Metal-working fluids (MWF) are susceptible to microbial contamination.
- Effective microbial control in large-scale MWF systems remains a challenge.
- Biocides are commonly used to manage microbial growth in MWF.
Purpose of the Study:
- To investigate microbial dynamics in a large-scale MWF system (150 m³).
- To assess the efficacy of biocide addition on microbial populations.
- To identify dominant microbial species and their growth patterns.
Main Methods:
- Monitoring microbial populations (CFU/ml) over time.
- Quantifying bacterial biomass using 3-OH lauric acid marker via gas chromatography.
- Identifying fungal and bacterial genera through culture and biochemical analysis.
- Assessing airborne microbial counts in the surrounding environment.
Main Results:
- Sustained high populations of Pseudomonas pseudoalcaligenes (>10⁸ CFU/ml) for a year despite biocide addition.
- Bacterial biomass estimated to be 15 times higher than viable counts.
- Dominance of Fusarium and Candida fungi observed.
- Massive P. pseudoalcaligenes regrowth upon fresh MWF addition, followed by enterobacteria and other gram-negative rods.
- Variability in P. pseudoalcaligenes morphology and biochemistry.
- Airborne bacterial counts inversely related to distance from machinery.
Conclusions:
- Standard biocide treatments may be insufficient to control P. pseudoalcaligenes in large MWF systems.
- Bacterial biomass can be significantly underestimated by viable counts alone.
- Fresh MWF can trigger rapid microbial blooms, altering community composition.
- Airborne microbial contamination is linked to MWF system operation and environmental factors.