Wisconsin Bioenergy Initiative | May 18, 2009 | Christine M. Lamm

One lab’s use of modern computers speeds up research on enzymes that break down the cellulose of feedstocks to produce ethanol.

Great Lakes Bioenergy Research Center (GLBRC) project co-leader and Associate Scientist, David Keating, is part of a research team focusing on improving the ability of microorganisms to convert cellulose to ethanol.

“This project is exciting to me because this is a deeply important problem and it also makes good use of skills I developed in graduate school and beyond.”

Keating has studied the metabolisms and physiology of microorganisms and views this research project as an opportunity for him to help benefit the country.

“The big picture is to develop microorganisms that are better in converting cellulose…whether it’s from corn stover or switch grass or whatever (feedstock) we choose.”

To efficiently produce cellulosic ethanol, sugars, primarily glucose, trapped within the cellulose of plants need to be extracted. Currently, however, there are no cost effective methods to extract these sugars from the cellulose -the primary problem for Keating and his research is in making feedstock conversions to ethanol economically viable.

The development of consolidated bioprocessors – single organisms which carry out all of the steps required for converting cellulose to ethanol – would lower conversion costs Keating said.

“It reduces costs because you don’t have to grow a bunch of different microorganisms, and you don’t have to add extra enzymes. You just have one bacteria (to add to) your feedstock…It’s almost impossible to break down cellulose…unlocking that potential is challenging, but microorganisms can break it down,” said Keating, “we plan to use that ability and couple it with ethanol production.”

Cellulase’s -secreted enzymes of bacteria that break down cellulose- chop cellulose into glucose bits that are then fermented to ethanol. This cellulase process is what needs improvement, Keating said. First, the enzymes currently available are expensive, which increases the cost of ethanol production. Second, the enzymes are inefficient, which means that large amounts of these expensive enzymes have to be used during the process.

“We are taking two broad approaches to develop consolidated bioprocesses of organisms: 1.) take a microorganism that normally degrades cellulose and endow it with the ability to make ethanol, or 2.) take an organism that’s good at making ethanol and then have to degrade cellulose. We do both because we don’t yet know which way is better.”

For example, much of the current studies in Keating’s lab make use of the bacterium E. coli.

“E. coli will produce ethanol. It is commonly used in fermentations, a lot is known about it, and it is a bacterium that’s easy to work with and manipulate. We are improving E. coli’s ability to bring sugars into the cells and convert them to ethanol…by improving its ability to secrete more cellulase’s.”

A key step in the development of these consolidated bioprocessing E. coli involves the use of a technique called multiomics, which provides a snapshot of the chemical reactions going on inside the E. coli cell. This information can then be analyzed by the use of computers.

“Using computers you can cluster the information, which then gets organized into a way you can take a look at it,” said Keating. “You take that data and make solid observations about why the (organism) is underperforming and how it can be improved.”

“In short, we can engineer bacteria that “need” to make more ethanol.”

Read the full article here.