Researchers Exploring Methods for Immobilizing Enzymes for Re-Use in Cellulosic Ethanol Processes

A South Dakota State University professor is exploring ways to re-use enzymes in processes such as making cellulosic ethanol. Working with enzyme company Novozymes, Dr. Basil Dalaly and his graduate student, Pavani Mandali, have evaluated several chemical methods to attach enzymes to beads. They then evaluated the enzyme activity, how well the enzymes attached to the beads, and other variables.

Enzymes are usually very expensive items in chemistry or biochemistry. One of the big obstacles in using enzymes in converting cellulose, or biomass, to ethanol is the high cost of enzymes. We are trying immobilize the enzyme by attaching it to beads. Afterwards, the enzyme could be used for more than one time — two, three, four, five times because the beads will keep the attached enzyme rather than allowing it to float away along with the processed products.

From our results so far I can say we are successful in using the enzymes for five cycles, but with decreasing activity from 100% to 40%. We still retain 40 percent of the original activity of the enzyme.

—Basil Dalaly

The ability to reuse enzymes would be a financial advantage in industrial processes that rely on enzymes.

Mandali, who is working toward her Ph.D. in biological sciences, said the SDSU research shows enzymes attached to the beads have 95% of their original activity when used a second time; 75% of their original activity when used for a third cycle; 50% of their activity when used a fourth time; and about 35 to 40% of their original activity when used for a fifth processing cycle.

The SDSU study is part of a many-pronged project to develop more efficient methods to produce ethanol from cellulosic biomass. The work so far shows the re-used enzymes work better on some biomass materials than others.

Dalaly’s work also looks at questions such as the time for all of the biomass to be hydrolyzed. The project also involves analyzing the hydrolyzed biomass to determine what monosaccharides are in the hydrolysate.

Dalaly said as the SDSU work continues he and his student will address the problem of how to gather or recover the beads once a processing cycle is over.

In addition to the enzymes provided by Novozymes, the federal Department of Energy and the South Dakota Corn Utilization Council help support Dalaly’s research though grants. The North Central Sun Grant Center at SDSU also funded some of Dalaly’s early work looking at enzymes in pretreatment of biomass feedstocks.


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