Microbes have been used in industry for a long time, principally for a process called fermentation. Fermentation is what happens when microbes use food for energy in environments without using oxygen.
Vinegar is made from the fermentation of alcohol in wine, cider, or even beer by acetic acid bacteria. Yogurt is made from bacterial fermentation of a sugar (lactose) in milk to produce lactic acid. A number of other products are made by bacterial fermentation including pepperoni from meat, sauerkraut from cabbage, and pickles from cucumbers.
In the laboratory we typically grow bacteria in petri dishes and test tubes, but in industry, bacteria are grown in much larger containers called fermenters, where they are used for a number of things.
Image from here.
Xanthan gum is a thickening agent found in food (e.g. salad dressing) and cosmetic products (e.g. shampoo). Xanthan gum is the EPS of the bacterial species Xanthomonas campestris. Xanthan gum is produced by growing huge Xanthomonas campestris cultures and then purifying the EPS.
Although Xanthomonas campestris naturally makes EPS, the strain used for industrial xanthan gum preparation is genetically manipulated to make it grow on whey, a cheap and readily available food source. Food industry scientists were scratching their heads over what to do with an excess of whey (a lactose-rich liquid by-product of cheese making). They decided to introduce genes into Xanthomonas campestris that would allow the bacterium to grow with lactose as a food source.
Most antibiotics were identified from microbes and, to this day, are produced in large cultures of either bacteria or fungi (a kingdom of eukaryotes). These bacteria or fungi are genetically manipulated to make sure they are producing a lot of the antibiotic quickly. Bacteria are used to produce a number of other drugs beyond antibiotics as well as the components of vaccines.
Another new application for microbes is the growing energy source of biofuels. Fossil fuels are made from the carbon remains of photosynthetic organisms that lived a long time ago, taking up energy from the sun and CO2 from the air. Of course, lots of plants are doing just that today, and represent a huge potential energy source, if we can learn how to tap it.
Scientists are investigating methods of biofuel production from a number of different angles.
Bacteria are obviously good at degrading things and growing in strange place. Many scientists are focused on finding ways to get bacteria (or some eukaryotic microbes) to break down leftover plant parts from crop harvests, such as corn stalks, into forms that are useful, safe, energy-rich fuels. Yet others are focusing on photosynthetic eukaryotic microbes themselves as the energy source.