Qi BioEnergy

Sugars are the essential raw material for a range of

biobased products from ethanol to bioplastics. In the

case of ethanol, sugar is converted into alcohol through

fermentation. Both corn grain and cellulosic feedstocks,

such as corn stover, straw and wood, are composed of

about 70 percent sugars, making them good candidates

for ethanol production. The challenge lies in extracting

the sugars from these agricultural feedstocks.

In corn grain, the sugars are all of the same variety (6-

carbon molecules of glucose), joined together with

relatively simple bonds to form starch. These simple

bonds can easily be broken using commonly available

amylase enzymes and water in a process called hydrolysis.

Isolating the sugars in cellulosic biomass is a

considerably more complicated task. Cellulosic biomass is

composed of a mixture of 6-carbon glucose sugars in the

form of cellulose and 5-carbon pentose sugars linked to

other 6-carbon sugars in the form of hemicellulose, all

held together by complex chemical bonds bound with a

stiff, fibrous substance called lignin. The biomass must

first be pre-treated to separate the lignin and loosen the

chemical bonds. Cellulase enzymes can then be used to

break the sugar-to-sugar bonds via hydrolysis.

Recent biotech advances have made significant

improvements in cellulase enzymes and pentoseprocessing

microbes, closing the gap on making cellulosic

biomass conversion to ethanol economical. As

commercialization proceeds, further gains will help ensure

sustainable feedstock platforms for fuels and chemicals.

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