What is one instance in which microbial metabolism has been harnessed to solve a real-world problem?

What is one instance in which microbial metabolism has been harnessed to solve a real-world problem? (Or is being researched as a solution to a real-world problem?)

To earn full credit, include the following in your answer:

1) the microbe or microbes used
2) details describing the metabolic process according to the terminology you have learned in class
3) describe how the microbial metabolism has been applied to solve the problem.