Microorganisms key to ethanol production

By MEREDITH MACKENZIE, UPI Correspondent   |   Feb. 23, 2006 at 1:18 PM
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"There are no technical barriers to making ethanol from woody material today," said Lonnie Ingram, a microbiologist and professor at the University of Florida.

Ingram said the goal of research like his is to make renewable energy from woody or cellulosic material such as sugarcane stalks, corn stalk and leaves, municipal grain waste, trimmings from trees moved for utility lines and debris from hurricane damage.

"These materials are typically buried in landfill. Why shouldn't we make energy materials from that?" said Ingram. "Corn may not be the optimal crop and there's certainly room for exploration."

In his State of the Union address last month, President Bush said the United States was "addicted to oil" and called for a diversification of U.S. energy sources, pointing to ethanol. As part of his push toward new sources of energy, Bush has echoed that message throughout the country.

"The problem is we need more sources of ethanol. We need more -- to use different products than just corn," he said Tuesday at the National Renewable Energy Laboratory in Golden, Colo. "And so one of the interesting things happening in this laboratory and around the country is what's called the development of cellulosic ethanol.

"That's a fancy word for using switch grass, corn -- wood products, stuff that you generally allow to decompose, to become a source of energy."

Much of that work is already being done at NREL.

Jim McMillan, a research scientist and microbiologist at NREL, and his team have developed an ethanologenic strain of zymomonas mobilis bacteria that can use two of the most abundant sugars in cellulosic material: glucose and xylose.

"It is one of the more promising strains out there," he said.

McMillan and other scientists around the world are experimenting on microorganisms used in the fermentation step of the ethanol-production process. First, woody materials like sawdust or agricultural waste are chopped up into small pieces. The material is then pretreated with enzymes to break down the complex sugars in the material into simple sugars, which are fermented with yeast or bacterial like E.coli into an alcohol fuel --ethanol.

"Finding organisms that are able to ferment biomass sugars to ethanol is a tremendous breakthrough," said McMillan of bacterial sources. "The next big challenge is to get them to exhibit the hardiness that yeast has."

Researchers at Purdue University led by Nancy Ho have genetically engineered a strain of Saccharomyces cerevisiae, more commonly recognized as brewers or bakers yeast to ferment the two main sugars from cellulosic material into ethanol.

"Regular yeast can't convert the single sugar to ethanol," said Ho. "For our yeast we just made sure that it did a little extra."

By genetically splicing properties from other microorganisms capable of fermenting the sugars xylose and glucose simultaneously, Ho's team has developed the hardiest fermentation agent being used in ethanol production today.

One company using the Purdue yeast is Canadian bioenergy corporation Iogen.

"We are optimizing the Purdue yeast, but we are not doing any further development at the moment," said Iogen's manager of biotechnology Theresa White.

One of White's responsibilities is to oversee research on one of the steps in the pre-fermentation process. She helps to cultivate a fungus, trichodrema reesei, which produces enzymes that break down the complex sugars in cellulosic material.

"The fungus is not a pathogen; it doesn't do anything but eat dead trees," she said. "... It is very safe and very efficient at breaking down cellulose.

"Nature evolves the enzymes to work in specific conditions and we are trying to make it work in a different condition."

Compared with the ability of yeast to withstand extreme pH, temperature and produce high concentrations of ethanol in fermentation, bacteria that can perform the same function need further engineering before they can be used at the same level.

"All the organisms we have now can only get to ethanol concentrations of 5 and 7 percent or 50 to 70 grams per liter," said McMillan of the bacterial organisms he is working with. "If we look at what we can do in yeast, we are able to make more than double that concentration right now."

He offered an analogy: "The strains of bacteria can make beer, but we need them to be able to make wine. The more dilute the ethanol is ... the more tanks you need, and that raises capital costs."

The start-up costs of a new large-scale industry that produces ethanol from biomass are high. The ethanol industry is currently focused on deriving ethanol from corn kernels.

"When it comes to biomass no one is collecting these things," said Charles Abbas director of Yeast and Renewal Research at Archer Daniels Midland Co. "You have to collect them in large enough quantities to be able to produce enough ethanol to make it sustainable. It is a huge, massive undertaking."

Abbas said the solution to this problem is to focus the fledgling industry on producing ethanol from biomass products that are already collected and which already have some market value.

"The near-term opportunity is in what is already being collected today. For example if you have a paper mill, you already have the sawdust and you know what the sawdust costs," said Abbas. "The fiber streams people are talking about, corn stalks, sugar cane, are not collected."

Besides that, said Abbas, these materials are high in moisture, making them heavy, thereby pushing up shipping costs to a range that prevents the industry from being competitive.

A joint study released by the Departments of Energy and the Agriculture in 2005, concluded the United States has the biomass resources to produce a sustainable supply of energy sufficient to displace 30 percent or more of the country's present petroleum consumption at the current rate of growth.

The study highlighted infrastructure and supply chains that would be needed to make an ethanol industry viable.

"Changes in the way biomass feedstocks are collected or harvested, stored and transported, and pre-processed will also have to be made," the report said. "Accomplishing these changes will obviously require investments and policy initiatives as well as the coordinated involvement of numerous stakeholder groups to gain broad pubic acceptance."

Ingram said he was pleased to hear Bush's commitment to renewable energy resources, but noted "one barrier" was building a first-of-a-kind plant.

Right now companies that produce ethanol from biomass have only small production demo plants. A pilot facility at Iogen can process up to 1 ton of ethanol a day on small-scale equipment. There is also a demonstration facility that has full-size equipment capable of processing 10 tons a day, but Iogen does not operate it at full capacity.

"It is set up so that you can optimize each unit operation and the whole process flow," said White. "It is the final validation before a full-fledged commercial operation is built and the design basis for commercial facilities.

"The plan is to develop that within the next three to five years."

A large-scale plant to experiment mass production and the economic viability of the industry is needed, said Ingram.

"What is needed is some form of business incentive to launch biomass ethanol as an industry," he said. "I really hope we see some actions in that."

Ingram's ideas to raise additional funding to support the biomass ethanol industry include a penny per gallon gas tax or "energy bonds" as a way for Americans to invest in the future of energy technology.

Ho, who said she did not intend to make the rights of the Purdue yeast exclusive, agreed that industry is limited because it is so new.

"Pretty soon it will be a viable energy source," she said of biomass ethanol. "But it's a new industry and it takes time to become established."

But, Ingram said, the best way to help battle U.S. energy addiction is conservation.

"We can make the biggest immediate difference in our consumption by conservation," he said. "We won't solve it by conservation alone, but we can do a better job using the materials we use today."


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