Scientists at the U.S. DOE's Brookhaven National Laboratory have successfully engineered an enzyme that can be used to break down the lignin in plant cell walls, making it easier to convert the plant material into cellulosic ethanol.

Biochemist Chang-Jun Liu said that while the research is in its early stages, the ultimate goal is to apply the enzyme to feedstocks such as poplar in order to make the plants more easily digested and fermentable at an industrial level. "We tested this concept; we transferred those genes into the plant, but right now all of the work is limited to the laboratory level," he said.

Liu's work has focused on lignin alteration because it represents a major barrier for cellulosic ethanol production, he said. "Increasing the digestibility of plant matter is one main approach to making plants a viable alternative energy source. Our group has been working to achieve that goal by elucidating the catalytic mechanisms of plant enzymes, and then using that knowledge and the tools of molecular biology and protein engineering to influence the way plant cell walls are constructed."

Using natural enzymes as a template, Liu and his team first examined the structural models of the enzyme and its genetic code before comparing the data with the same information from enzymes involved in lignin synthesis. By comparing the data, the team identified the optimal alteration points and used that information to build a new enzyme model. The final enzyme prevented the plant cell's lignin precursors from linking up to form lignin polymer.

Liu said Brookhaven's engineered enzyme is novel and is "totally changed" from the naturally occurring enzymes that were used as a template. "Our hope is that this will introduce a new step at the end of the normal lignin biosynthetic pathway and redirect synthesis from the conventional lignin precursors to the specifically methylated ‘dead' products to yield less lignin," he said, adding that the team still needs time to determine exactly how the enzyme will affect lignin biosynthesis.

The DOE's Office of Science is providing funding for Liu's continued research and experimentation.

SOURCE: ETHANOL PRODUCER MAGAZINE