Good bacteria in MWF

Using "good bacteria" to fight bacteria that destroys the metalworking fluid sounds great in theory, but there are many risks associated with this strategy. 

There is a trend to allow bacteria in metalworking fluids because you can’t see that the fluid had any immediate negative consequences of the bacteria. There are also suppliers that add so-called good bacteria in the MWF to keep worse bacteria away.

I think that to even consider the method with good bacteria, you have to ensure that no employees have compromised immune systems and be prepared to make analyzes of each system at least once a week.

One of the common good bacteria is Pseudomonas pseudoalcaligenes, so let’s take a closer look at it.

1. Pseudomonas pseudoalcaligenes are opportunistic pathogenic, meaning they can be very dangerous for people with compromised immune systems. A study in Canada showed that the soap bubbles that were given to children in hospital made several of the children seriously ill, because the bubbles contained Pseudomonas pseudoalcaligenes.
2. If the conditions varies, the composition can change can rapidly and Pseudomonas pseudoalcaligenes is no longer the dominant species. It is an aerobic bacterium, which means it require oxygen to grow. If the oxygen level in the fluid is reduced, for example if the machine have been standing still during the weekend or if the separation of leaked oil is poor, other species will probably thrive and can take over as the dominant flora. Normal tests is not enough to distinguish pseudoalcaligenes from other species, it requires advanced lab equipment such as PCR (Polymerase Chain Reaction).
3. Pseudomonas pseudoalcaligenes is a gram negative bacterium which can generate endotoxins. Endotoxin is toxic substances found in the cell wall of bacterial species and is released mainly when the bacterial cell bursts. Endotoxin activates the immune system and may even lead to endotoxic shock. Dr. Frederick Passman has an interesting post about endotoxins here.
4. Even good bacteria are consuming components of the metalworking fluid and contributes to coating on machinery and tools, and to an increased filter consumption.

(JÖ)