Novel Pretreatment Reduces Binding of Enzyme with Altered Cellulose but Increases Sugar Yield

Increased binding of enzymes to cellulose does not necessarily lead to more efficient conversion into simple sugars, according to a recently published study by researchers at the Los Alamos National Laboratory (LANL) and the Great Lakes Bioenergy Research Center (GLBRC).

The researchers found that when cellulose is converted to a unique crystalline structure called cellulose III using a novel biomass pretreatment, the binding ability of native cellulase enzyme that targets cellulose decreased but the sugar yields from cellulose breakdown increased by as much as five times.

The researchers only recently discovered the increased sugar yield from cellulose III. The efficiency of biofuel production is tied to the amount of fermentable sugars released from cellulose breakdown. Unlike the untreated cellulose, cellulose III was found to have a less sticky surface that makes it harder for native cellulase enzymes to bind. 

By developing a kinetic model explaining the relationship between enzyme affinity for cellulose and catalytic efficiency, the researchers were able to predict that the enhanced enzyme activity, despite reduced binding, is due to the relative ease with which enzymes are able to pull out individual cellulose III chains from the pretreated cellulose nanofiber surface and then break them apart into simple sugars.

The new research findings, published in the Proceedings of the National Academy of Sciences, open up avenues to engineer novel cellulase enzymes that are tailored for conversion of cellulose III-rich pretreated biomass to cheaper biofuels.