The enzyme thatbreaks down cellulose, one of the most common carbohydrates on planet Earth.
No naturally-evolved Earth mammal can digest cellulose, though some (such as cows and other ruminants) have a symbiotic relationship with bacteria which can. In the early centuries AT cellulose-digesting bacteria capable of living in the human gut were engineered. This allowed humans equipped with such bacteria to digest cellulose as well as any cow, and thus live on things people without them could not. The distribution of this bacteria across humanity was a major cause of the world-wide reduction in famine which took place in those years. Additional bacteria engineered to digest lignin (ligninases) were also added, and provided a means for humans to digest even wood (when suitably prepared!), and similar bacteria to digest even more formerly-indigestible forms of organic matter were created over time. In later years genes for cellulase, ligninase and so on were engineered directly into some types of humans, sometimes in large numbers, allowing them to survive on, and digest, a much wider range of foods than in their baseline state.
Text by Tony Jones
Initially published on 24 September 2001.