Turning Grass and Trees into Food: Neo-Malthusians Mocked by Human Ingenuity Again


More parts of a pine tree are edible
Credit: Dreamstime

During famines, desperate people often try to survive by eating things like grass and tree bark. That doesn't do much to alleviate their hunger since trees and grass are chiefly composed of cellulose which people's guts cannot digest. Starch, found in wheat, corn, rice, and potatoes, makes up a big portion of the modern human diet. Now researchers at Virginia Tech have announced in The Proceedings of the National Academy of Sciences that they can turn cellulose into edible starch. From the abstract:

The global demand for food could double in another 40 y owing to growth in the population and food consumption per capita. To meet the world's future food and sustainability needs for biofuels and renewable materials, the production of starch-rich cereals and cellulose-rich bioenergy plants must grow substantially while minimizing agriculture's environmental footprint and conserving biodiversity. Here we demonstrate one-pot enzymatic conversion of pretreated biomass to starch through a nonnatural synthetic enzymatic pathway composed of endoglucanase, cellobiohydrolyase, cellobiose phosphorylase, and alpha-glucan phosphorylase originating from bacterial, fungal, and plant sources. A special polypeptide cap in potato alpha-glucan phosphorylase was essential to push a partially hydrolyzed intermediate of cellulose forward to the synthesis of amylose. Up to 30% of the anhydroglucose units in cellulose were converted to starch; the remaining cellulose was hydrolyzed to glucose suitable for ethanol production by yeast in the same bioreactor. Next-generation biorefineries based on simultaneous enzymatic biotransformation and microbial fermentation could address the food, biofuels, and environment trilemma.

R&D Magazine further notes:

Cellulose is the supporting material in plant cell walls and is the most common carbohydrate on earth. This new development opens the door to the potential that food could be created from any plant, reducing the need for crops to be grown on valuable land that requires fertilizers, pesticides, and large amounts of water. The type of starch that Zhang's team produced is amylose, a linear resistant starch that is not broken down in the digestion process and acts as a good source of dietary fiber. It has been proven to decrease the risk of obesity and diabetes.

Thus does human ingenuity conjure new resources and mock the grim prophecies on Neo-Malthusians.