If you've ever made kombucha, you will be familiar with the term SCOBY—a symbiotic culture of bacteria and yeast. It's impossible to miss—it's the floating biofilm on top of your delicious drink.

Cellulose, the most abundant natural polymer, also gives distant cousins of paper—woven cotton textiles such as T-shirts and blue jeans—the durability, comfort, and water absorbency that we look for ...