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Generating bioethanol with starch and yeast

Starch is a polysaccharide found in food and plants. Finding ways to effectively break down all forms of starch, into usable sugars, is seen as key for the effective production of biofuels.

Biofuels include fuels manufactured from biomass conversion (such as plant matter.) Cellulosic biomass is derived from non-food sources, such as trees and grasses. There are ethical issues surrounding the use of biofuels. For example, crops that could be used to feed people are used to provide the raw materials for biofuels instead. The use of non-food sources gets around this issue; however, this brings with it some environmental concerns.

In terms of the process, starch as a key part of the collected biomass can be used as a feedstock for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Modern petrol engines can use petrol containing up to 10 percent ethanol without needing any modifications.

Bioethanol is manufactured by yeast fermentation of sugar. Any carbohydrate or biomass can potentially be turned into glucose sugar and used as raw material. At present it is mainly sugar and starch in agricultural crops, such as sugar cane, maize and cassava that are used. A second generation ethanol produced from this process is termed cellulosic ethanol, as distinct from bioethanol. The performance of the two ethanols is similar, the difference being the production method.

The new class of enzymes are termed lytic polysaccharide monooxygenases (LPMOs). These enzymes are secreted by certain fungi and bacteria. The process works by the enzymes drawing oxygen from the air to trigger an oxidation process, which breaks down the starch biomass. The technical term used to describe this, according to the authors, is “valorize.” The enzymes themselves are described as “wedge-like copper-dependent metalloenzymes.”

The study was carried out at the University of York and the findings have been published in the journal Nature Communications. The research paper is called “Structure and boosting activity of a starch-degrading lytic polysaccharide monooxygenase.”

Written By

Dr. Tim Sandle is Digital Journal's Editor-at-Large for science news. Tim specializes in science, technology, environmental, and health journalism. He is additionally a practising microbiologist; and an author. He is also interested in history, politics and current affairs.

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