Aerobic & Anaerobic Bioremediation

Instructor: Angela Hartsock

Angela has taught college Microbiology and has a doctoral degree in Microbiology.

Organisms that participate in bioremediation can metabolize pollutants in the presence and absence of oxygen (aerobic versus anaerobic). Knowing which process is occurring can help us support bioremediation.

Bioremediation and Metabolism

Cleanup of environmental pollutants is a major problem facing humanity. The logistics and cost of cleanup can be overwhelming. Thankfully, we have some natural helpers out there. Bioremediation is the metabolism or immobilization of environmental pollutants by biological organisms. When organisms use a chemical compound for metabolism, they either break it down for energy or modify the chemical so they can use it for growth or cell maintenance. During bioremediation, organisms like bacteria and fungi can produce protein molecules that catalyze chemical reactions, called enzymes, that break down environmental pollutants.

Aerobic versus Anaerobic

Even tiny organisms like bacteria and fungi can breathe. When organisms break down environmental contaminants for energy, the process is typically linked to the respiration (the breathing) of either oxygen or some other inorganic molecule. When an organism requires oxygen to break down an environmental contaminant, we call that aerobic bioremediation. And, when an organism carrying out bioremediation can breathe some other molecule besides oxygen, we call that anaerobic bioremediation. The an- part means without or lacking, and the aerobic part refers to oxygen. So aerobic uses oxygen, and anaerobic doesn't.

When an organism that carries out aerobic bioremediation has oxygen and a contaminant available, it is love at first sight. The organism has energy for growth and reproduction and we are happy because that means the contaminant gets broken down and removed from the environment.

Illustration of the difference between aerobic and anaerobic bioremediation
illustration of aerobic and anaerobic bioremediation

When an organism that carries out anaerobic bioremediation has a contaminant and some other molecule (not oxygen!) to breathe, it is loving life. There is energy available for the organism to grow and reproduce with the contaminant serving as the food source. The trick in anaerobic bioremediation is that the organisms typically can't carry out bioremediation if oxygen is present. In many cases oxygen interferes with the production or activity of the enzymes needed for anaerobic bioremediation.

Environmental Conditions

Now that we have an idea of how aerobic and anaerobic bioremediation work, let's think about what's happening in the environment. Environmental conditions are constantly changing. There are lots of organisms living out there that could aid us in bioremediation, depending on what kind of enzymes they make and on the environmental conditions.

We can imagine a contaminated soil environment (Environment 1) that has oxygen present. Among the many organisms living in the soil, there are two, the pink and the green, that have the ability to break down the contaminant. The trick is that the pink organism can break down the contaminant using oxygen and the green one breaks down the contaminant without using oxygen (and can't do it if oxygen is around). So, in this case the pink organism will carry out aerobic bioremediation and be responsible for helping us get rid of the contaminant.

Example environments for aerobic and anaerobic bioremediation
Two example environments

Now, let's imagine another soil environment (Environment 2) where the same contaminant is present, but now there is no oxygen in the soil. In this case, the pink organism isn't going to have oxygen to support aerobic bioremediation, so it isn't going to be contributing to removing the contaminant. But now, if there is another molecule available for the green organism to breathe, it can step in and break down the contaminant (anaerobic bioremediation). In both environments we end up with the same outcome; the contaminant gets broken down. However, that process happens in very different manners and by different organisms depending on the environmental conditions.

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