I’ve seen this false assertion all over the internet. Louis Pasteur must be turning over in his grave! Bacteria do not produce feces as we know it. They do excrete by-products of their metabolism such as carbon dioxide, however, I believe at the heart of your question is the use of bacteria or other microorganisms to produce food ingredients, including aspartame.
It would be hard for us to find much to eat without microorganisms. Bacteria, fungi and algae—all have been used in food production for a long time, even before humans knew why their role was so critical. They are used to make hundreds of the foods we eat, including bread, yogurt, wine, beer, cheese, vinegar, meats, chocolate, coffee, tea, tofu, ice cream, mayo, fish, sausage, pickles, olives, butter, juices, some vitamins and other supplements, and many, many more.
The roles of these microorganisms in food production are varied. They can be used to improve nutritional value (some essential nutrients added to breakfast cereal are produced by bacteria), for fermentation (beer is brewed with yeast and/or bacteria), to add taste or flavors (ice cream, margarine, jelly; this is also yeast’s role in bread making in addition to leavening and gluten production), to thicken, emulsify or stabilize food (e.g., bread, chewing gum, soft drinks, peanut butter, cakes, frozen desserts, sauces, mayo, even toothpaste, although I haven’t eaten that in a long time). These microorganisms can be GM or non GM.
In the manufacture of some foods, whole microorganisms are used. In others, the food can contain purified products made by microorganisms. The latter is the case in the cereal example above, and for enzymes, colors, flavors, and sweeteners including aspartame. Again, these microorganisms can be GM or non GM. The precursor to aspartame is produced by bacteria, isolated, purified, and chemically combined. The final product (aspartame) is subject to further purification. Whether the manufacturer uses GM or non GM bacteria to make aspartame, or any other food ingredient, no trace of the bacteria is present in the final product. A good description of the aspartame production process can be found at www.madehow.com.
It’s important to note that the process of exploiting bacteria’s metabolic capabilities to produce the products we want is not limited to the production of foods. Pharmaceuticals we use every day—vaccines human insulin, human growth hormone, antibiotics, certain anti-cancer drugs and more—are made in a similar fashion, largely from GM microorganisms. Microorganisms are also used in many other sectors, including forestry, textiles, cosmetics, energy, pulp and paper, mining and waste treatment.