A unique approach to The Challenge Test
Why is microbiology relevant in the lubricants industry?
For years the lubricant industry has faced microbiological contamination problems in metalworking when using O/W (oil/water) emulsions.
The high-water content (>90%) as well as the chemical composition of metal working fluids provides a favorable habitat for bacteria and fungi. The bacterial degradation of metal working fluids leads to the loss of key properties: changing viscosity or pH, causing corrosion and reducing lubrication performance. Anaerobic bacteria, bacteria that doesn’t live or grow in the presence of oxygen, can produce hydrogen sulfide and other gases. Excessive microbial growth, especially fungal growth, can result in clogged filters and can interfere with metalworking operations.
More importantly, bacterial and fungal proliferation is a potential threat to workers’ health. Contact with microorganisms can lead to respiratory and skin diseases: bacteria able to survive in metal working fluids, such as enterobacteria or species of the genera Pseudomonas and Mycobacterium, are often potentially pathogenic.
Bacteria and fungi can be introduced into metal working fluids by the water used, by inoculation from biofilms formed in hoses or pipeworks, by personnel handling the machines or by particles or aerosols. Poor fluid maintenance is often the reason for the spread of such microorganisms.
Many years ago, it was found that the standard methods for microbiology utilized by the cosmetics, pharmaceutical or clinical industries were not directly applicable in the field of lubricants. Products easily passed conventional resistance tests such as the Challenge Test, but still failed to resist bacterial contamination when used in the customer’s own facilities. This led FUCHS LUBRICANTES S.A.U. to develop its own methods based on the standard ones. Director of Research and Development, Gema Del Olmo, was instrumental in the adaptation of the revised Challenge Test. “When I joined FUCHS in 1997, I worked in the development of new soluble cutting fluids without boron and one of the challenges of the new technology was to provide good microbiological resistance,” says Del Olmo. “I had to ‘create’ some tests to check this property and I developed the first ’challenge test’.” Variations of the test included the addition of extra nutrients to support microbial growth and the use of bacteria isolated from real contaminated fluids instead of bacteria from culture collections.
FUCHS team members check the growth of pseudomonas.
Today’s Challenges
In coordination with its R&D department, the FUCHS LUBRICANTES S.A.U. laboratory is currently focused on two main areas of work.
In one area, technical managers receive support from the Microbiology Laboratory, thereby providing added value to FUCHS products and helping to manage processes for FUCHS customers. The Microbiology Laboratory can isolate and identify recurrent contamination (fungi, yeasts or bacteria) by using conventional microbiology techniques and, in collaboration with the Hospital Clinic of Barcelona MALDI-TOF, biochemical tests or staining and microscopy observation
In 2016, the laboratory purchased an ultra-freezer (-80ºC), to preserve the isolated microorganisms for later use. The long-term preservation of bacterial strains is a key issue, as all testing is made using autochthonous adapted strains. In addition, biocide effectiveness can also be evaluated using fungi and bacteria isolated from the field, either for treatment or in-product protection. This is done through the use of adapted clinical microbiology tests such as the Kirby-Bauer test or MIC-MBC tests.
In the other area, the Microbiology Laboratory provides services to all FUCHS R&D departments worldwide, mainly assessing the resistance of FUCHS products to microbial contamination. “The knowledge about our products and the indication of their probable performance in use is a key feature,” says Dr. Eulàlia Martínez Pascual, Head of the Microbiology Lab at FUCHS LUBRICANTES S.A.U. “The development of more resistant soluble products will lead to better performance, with fewer incidences of contamination, and hence a longer product lifespan.”
In recent years, changes in legislation on biocides (BPR) and the classification of substances (CLP) have led formulators to switch to new technologies for less aggressive products. The new formulations are tested in the FUCHS Microbiology Laboratory using the adapted challenge tests to determine optimal compositions. Product technical development, as well as new requirements and needs, make it absolutely necessary to develop and improve the methods used.
FUCHS scientists evaluate fast-detection methods for identifying bacteria.
One FUCHS expert observes a sample in a microscope, while the other prepares cultures for sample testing.
Since 2016, FUCHS has adapted the Challenge Test for use in applications other than metal working fluids. Changes in legislation have also affected other product specialties such as quenching, mining or construction and many products have been adapted to the new requirements. This means that new chemicals, with a potential impact on product stability and performance, have been introduced into formulations making it necessary to ensure that the properties of the products remain unchanged. “One of the advantages we have with the microbiology lab is that we can assess the behavior of our products. In our internal process, we are sure that our products are not contaminated and our customers can be satisfied that during the use of our products, their emulsions are safe (when properly handled)”, says Del Olmo. “Thanks to the challenge test we can check every modification of our formulations and any new development making sure that the microbiological resistance is tops and at the right level for our customers’ needs. We can compare different products and technologies and choose the best option for every application. We can also look for limit concentration of use (the minimum concentration at which customers should work to guarantee there will be no problem in contamination).”
To evaluate their applicability to in-use lubricant samples, the laboratory is constantly pursuing rapid detection methods. Lubricants are a very complex matrix and the available methods face detection issues, so their effectiveness, accuracy and speed need to be carefully evaluated. Several existing methods have been tested in recent years.
Future Goals
The future brings other goals such as developing methods for rapid microorganism detection to improve service.
Resistance to biofilm formation is another important topic. Biofilms are the prevailing habitat for bacteria in most environments, where they grow and adhere to a surface. Biofilms can cause failure in machines and centralized systems, and act as a continuous source of bacteria in metal working fluids. Knowing how to prevent their formation and how to eliminate them can make a difference for FUCHS competitively
The Microbiology Laboratory is open to new challenges driven by changes in legislation and market trends, always focusing on serving the entire FUCHS group and FUCHS customers in getting to grips with the nuts and bolts of microbial degradation.
