CSI Says New Pretreatment Technology for Cellulosic Biomass Could Reduce Enzyme Dosage By Up To a Factor of 10
Researchers at Cellulose Sciences International (CSI) have developed a pretreatment technology of cellulosic biomass to reduce its recalcitrance (resistance to breakdown into sugars), enabling possible significant increases in rates of conversion of celluloses to sugar by cellulase enzymes, with an accompanying decrease in the required dosage of the enzymes. This, in turn, could lower the production cost of cellulosic biofuels and chemicals.
In a presentation of the work at the 239th National Meeting of the American Chemical Society, Dr. Rajai Atalla, founder of the company, said that CSI has achieved conversions on the order of 80% in approximately 20 hours for bleached kraft pulps; conversion of a control was 45%. For corn stover, they have achieved conversion rates that are twice those of controls, Atalla said.
We believe our finding will have a major impact on the economics of cellulose to biofuels conversions. We think it can make cellulose significantly more competitive with corn as the primary source of glucose as a feedstock for biofuels. Using this new technique, we expect that we will be able to reduce the prerequisite dosage of enzymes by a factor of 10, which could bring the cost of enzymes for cellulose conversion to the same level as that for corn.
—Dr. Rajai Atalla
The basis of the new technology is a procedure for decrystallizing cellulose into a form stable in aqueous media and suitable for enzymatic hydrolysis. CSI says that such decrystallization opens up structure at the nanoscale level; enhances accessibility for enzymes; and enhances the rates of enzymatic conversion of cellulose to glucose and soluble oligomers to a degree that leads to the reduction of required residence time for
enzymatic hydrolysis and the correlated capital investment associated with long residence times.
In the study presented at the ACS meeting, CSI used Avicel as a substrate. Avicel—a tradename that has become used as a generic—is a microcrystalline cellulose that is made by hydrolysis of high purity bleached kraft pulps followed by mechanical fragmentation; it is highly recalcitrant.
The CSI involves the use of NaOH dissolved in a co-solvent mixture of ethanol and water. When the NaOH is washed out with the water, the cellulose is converted to the mercerized form, which is even more resistance to hydrolysis than the isolated native forms. But if the NaOH is washed out with the co-solvent mixture, CSI says, the structure remains open. The co-solvent used to wash out the NaOH can be re-concentrated and the co-solvent and the NaOH can be recycled, to there are no significant consumables.
Resources
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An Innovative New Technology to Reduce Recalcitrance of Cellulose
and Make it Competitive with Corn as a Biomass Feedstock -
Rajai H. Atalla, Rowan S. Atalla (2010) Cellulose recalcitrance during enzymatic hydrolysis: Its induction during isolation and its reversal using an innovative new technology (ACS 239)
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Rajai H. Atalla (2010) Structures of native celluloses: An assessment of the experimental data and their implications (ACS 239)
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