The formula for glucose is $\ce{C6H12O6}$ and that of cellulose is very similar $\ce{C6H10O5}$. Glucose can be readily fermented by yeast and other micro-organisms to produce carbon dioxide and ethanol. Whereas cellulose is not ferment-able by yeast and only very specific anaerobic Archae bacteria can digest it, but the end product being methane, water, sugars (primarily lactose), and volatile fatty acids (acetate, proprionate, butyrate); not ethanol. These bacteria reside in the guts of termites that allow them to digest wood, and in the intestines of cattle and other ruminants. The termites and ruminants use the sugars and fatty acids as food.
The enzymes used by the host anaerobic bacteria in the gut of termites are of particular interest because:
- termites produce very little solid waste as feces
- termites can digest wood, leaves, and broader variety of plant fodder than ruminants, which mainly feed on grasses
We are not really interested in the termites, nor the anaerobic bacteria, but rather specifically the enzymes and chemical processes used by the bacteria that break down the cellulose into the lactose and fatty acids. Can this be accomplished synthetically in an anaerobic lab setting outside of said bacteria?
This article describes a company that tried to use cellulose raw material to produce ethanol on a commercial level, but recently went bankrupt. This company apparently was not getting ethanol directly from fermentation of cellulose but rather the result of a multiple step process of generating syngas from the cellulose, then creating alcohol from the syngas; a much less efficient process than direct fermentation of cellulose into alcohol.
Obviously, such a process if achievable would relieve the need to use food crops to generate ethanol and put to use otherwise inedible cellulose plant waste. What is the main challenge here. Cellulose is just one water molecule different from glucose.