|MadSci Network: Cell Biology|
This is a good question. Introducing cellulose digestion into humans would be very difficult. We're definitely not going to be genetically engineering any humans, so we have to think about how we could genetically modify the bacteria that digest. In the rumen of cattle, the most active cellulose digester is Fibrobacter succigenes which is responsible for 50% of all cellulose digestion. Obviously other bacteria participate in this digestion. In addition, the gut of termites contain both protozoa and bacteria which may both be involved in symbiotic cellulose digestion.
These bacteria could not survive in our stomachs, due to the harsh acidic environment. Also, the fact that we have not already assimilated these organisms argues against their survival in humans. If these bacteria/protozoa were to somehow survive the stomach, they would have to deal with the onslaught of antibodies and immune cells present in our intestinal epithelium. In addition,the fact that our guts are already packed with symbiotic bacteria would make it very difficult for these cellulose-digesting organisms to establish themselves. Trying to stop this immune attack would be very difficult because not only would we make ourselves more habitable to these organisms, but also possibly other detrimental organisms. So, adapting these bacteria would probably prove to very difficult.
I think it would probably be easier to simulate the guts of ruminants in a large fermentor and throw in a bunch of cellulose. This may produce usable food like sugars.
Try the links in the MadSci Library for more information on Cell Biology.