Industrial Microbiology Consulting
Odor & slime problems lead to off spec products caused by bacteria & fungi. Environmental microbiology ]
Bacteria that grow in the absence of oxygen are called anaerobes. These can produce flammable gases such as hydrogen, hydrogen sulfide and methane and also malodors that cause community complaints as well as rejected products.
Anaerobes are more difficult to detect than the aerobic bacteria that easily grow on typical plating media such as 3M Petrifilms or routine agars. Anaerobes produce little ATP per glucose molecule compared to aerobic bacteria which make this common metabolic indicator less reliable in a highly reductive process. Specialized media and equipment may be needed to monitor these organisms.
Anaerobes are commonly found in chests with extended dwell times. They are found in processes that run at higher temperatures (40-55 C) where the high temperatures lower the dissolved oxygen content of the fluids. They are found within biofilms, particularly at the base of the biofilms where they can corrode soft metal. Anaerobic bacteria are also found in stagnant waters.
The US Chemical Safety Board produced a video on the dangers of conducting hot work (welding) in areas where anaerobic bacteria could produce explosive gases.
Signs of potential anaerobic growth include:
Decrease in Oxidation Reduction Potential (ORP)
Rotten egg aroma (hydrogen sulfide)
Volatile fatty acid aromas (acetic, butyric, propionic, valeric acids)
Readings of lower explosive limit (LEL) using a meter
Decrease in pH across a tank or chest
Consults on anaerobic bacteria odor, industrial microbiology, and biocide