Starch and cellulose are both polymers of glucose produced by plants and both are insoluble in water. Plants create cellulose to form their structure and once glucose molecules have been strung together by the plants to make fibers (wood is the most salient example). it is unavailable to the plants for any future chemical manipulation. Plants store starch in their roots, seeds and deep layers of the bark as the source of energy and material for growth spurts as when seeds germinate or perennial plants put on their annual spring growth spurt. Glucose is formed in green plants from carbon dioxide in the air and water from the soil. This chemical reaction does not proceed spontaneously because it requires a source of energy. In nature, this energy is supplied by the light of the sun with an assist from chlorophyll. The glucose travels dissolved in sap to the root, bark or seed for storage where it is converted to starch for future use as structure and energy to create the new structures.
When animals need energy, they eat
plants (or each other). Only a few kinds
of animals can obtain energy from cellulose and only with assistance of
bacteria in their digestive tracts.
Ruminants do it with their multiple stomachs containing the necessary
bacteria and their cud chewing to increase the contact
time of the cellulose and the bacteria because even the bacteria can digest
cellulose only slowly. Horses, elephants
and rabbits do it less efficiently by harboring the necessary bacteria in the cecum, the upper part of their large intestines. Incidentally, if you deliver a calf by
caesarian section and keep it in a sterile environment, it cannot digest
cellulose until you release it into our dirty, bacteria-containing world. The hoatzin, a beautiful auburn colored bird
Termites also digest cellulose with the assistance of bacteria. When I was in school, it was not known how they managed it in their tiny bodies. It turns out that they also require a variety of swimming one-celled animals with a hairy surface to harbor the bacteria. These swimming one-celled animals are called paramecia (just one of them, a paramecium). By swimming upstream in the termite’s intestine with their resident bacteria, they help the bacteria avoid being expelled and increase the contact time with the cellulose to be digested.
At a session of the AAAS (American
Association for the Advancement of Science) February 15, 2003, on sustainable
development an expert from Brazil on ethanol production in industrial quantities
described how they had succeeded in switching a significant fraction of their
automobile fleet to 100% ethanol fuel.
Since discovering petroleum off the northeast coast of
Cellulose has been converted to glucose using heat in an acid medium, but it is not cost effective so far at least partly because it has to be done in batches neutralizing the acid before introducing yeast for the fermentation of glucose to ethanol. In general, continuous processes are more economical than batch processes on an industrial scale.
A suggested remedy: Create an industrial sized termite intestine complete with paramecia and cellulose digesting bacteria, put the chopped or powdered crop waste (cellulose) in the front and get glucose solution out, ready for the same fermentation process now done in ethanol factories using sugar cane or corn.
Addendum:……Getting biomass ethanol from the laboratory to the
highway has been slow. BC International
of Dedham, Massachusetts, which plans to build a plant in
U. S. news and World Report,
Microbiol Biotechnol (2003) 61: 1-9 describes termites in great detail. Most of the 20 or so organisms that help termites to digest cellulose have not been cultured, but some have been identified by PCR (polymerase chain reaction), and presumably some are awaiting discovery. The bottom line: the products of termite digestion of cellulose include acetate, methane, hydrogen, and little or no glucose. So a giant ruminant stomach substitute looks more promising than trying to imitate termites for alcohol production. However, these mind experiments have been diverting. I still like the idea of using waste instead of a food crop. In the future, when I stray from medicine and health, I will pause a little longer for more research before going public.
Our daughter was riding with
When we get washing machines, most of us don’t get the full advantage of the labor saving device because we wash more stuff more often using up much of the time and effort we might have saved. Riding lawn mowers permit the same “wheel spinning” compulsion.
And when we get good roads and automobiles, many of us spend two hours per day commuting—ample time to put in quite a large garden resulting in great health improvement for the entire family.
John A. Frantz, M.D.