Mission

Background

Why Yeast?

Urgent Tasks

Initial Phase of Activities

Second Phase of Activities

How to Finance GIFC Activities

Consultant and Collaborator

About
Dr. Nancy Ho

Background

In the 1970s, the world suffered its first energy crisis.  As a result, governments worldwide, particularly the US Government, strongly supported the development of alternative fuels for transportation, particularly a renewable liquid fuel that could be produced from domestically available renewable resources. Ethanol has been proven to be a desirable renewable liquid fuel for transportation. In particular, ethanol can be produced by not only fermenting sugars derived from food crops such as cornstarch and cane sugar, but also from cellulosic biomass.  Cellulosic biomass (corn stover, rice straw, wood, grasses, waste papers, etc.) is the largest renewable resource in the world and is the most attractive feedstock for the production of ethanol fuel via microbial fermentation of its sugar molecules. 

The United States and many other parts of the world have tremendous amounts of cellulosic biomass, and more than 70% of this resource can be converted to sugars and fermented to ethanol by microorganisms, preferably Saccharomyces yeast.  However, the conversion of cellulosic biomass to ethanol requires the development of new technologies.  In particular, cellulosic biomass contains polymers comprised of two major sugars - glucose and xylose.

The Saccharomyces yeast, also known as baker’s yeast, is the most effective microorganism for the fermentation of sugars to ethanol.  It has been used for the production of wine and the baking of bread since the dawn of civilization.  The traditional feedstocks for ethanol production, cornstarch and cane sugar, contain polymers of glucose or simpler molecules made of glucose and fructose, which can all be effectively fermented by the Saccharomyces yeast to produce ethanol.  Saccharomyces yeast has been the only microorganism used for the large-scale industrial production of ethanol.  In general, the Saccharomyces yeast has far superior system in fermenting various sugars, not just glucose, to ethanol.  Furthermore, the yeast has other characteristics making it the most outstanding and desirable industrial microorganism for the production of ethanol (Why Yeast).  Unfortunately, the Saccharomyces yeast was found unable to ferment xylose to ethanol.

In the 1970s, research efforts were carried out worldwide in search of new yeast to ferment both glucose and xylose to ethanol.  However, no such ideal natural Saccharomyces yeast were discovered.  Thus, in the early 1980s, a concerted effort by scientists in various countries, particularly in the United States, Europe, and Japan, was made to use recombinant DNA techniques to modify the Saccharomyces yeast to ferment xylose to ethanol.  In the beginning, there were nearly ten groups worldwide focused on developing such recombinant yeast with at least half of the groups in the US.  One such group was the Molecular Genetics Group at Purdue University, West Lafayette, Indiana, led by Dr. Nancy Ho. This task turned out to be more difficult than initially anticipated.  Most experts concluded that it might not be possible to engineer the Saccharomyces yeast to ferment xylose.  This was potentially compounded by the fact that after the oil crisis eased in the mid-1980s, it became more difficult to obtain funding (in the United States) for research to develop alternative fuels. By the end of the 1980s, there were only four groups worldwide continuing in this endeavor.  Dr. Ho’s group was the only US group that continued to develop such recombinant yeast.  According to her analysis and design, she felt that the Saccharomyces yeast could be genetically engineered to ferment xylose. She also wanted to exhaust all possibilities before giving up because the Saccharomyces yeast has always been the safest and most effective microorganism for the conversion of sugars to ethanol. Furthermore, she felt very strongly that renewable cellulosic biomass should be utilized and converted to ethanol or other chemicals.  Thus, Dr. Ho persisted with great determination. Fortunately, by then her group had established a great reputation in the genetic engineering of industrial microorganisms.  Quite a few companies had asked her to upgrade their microorganisms and provided financial support to her group. This allowed her to continue the yeast xylose-fermentation project as funding allowed without jeopardizing the existence of her group. Her group has been entirely dependent on outside funding for all its expenses – including the salary of her personnel.

In the long run, her persistence paid off.  In 1993, Dr. Ho’s Purdue group succeeded in the development of the world’s first genetically engineered yeast that could effectively ferment xylose to ethanol.  In addition, her yeast, known as the Purdue Yeast, was also designed to effectively co-ferment a mixture of glucose and xylose together to ethanol, which is a crucial requirement for the efficient conversion of the major sugars present in cellulosic biomass.  This was accomplished by cloning three modified genes, XR, XD, and XK that are important for converting xylose to ethanol into the yeast.  The Purdue Group has continued to improve the Saccharomyces yeast with the goal of developing recombinant yeast ideally suited for large-scale industrial production of cellulosic or cellulose ethanol (ethanol produced from cellulosic biomass).  In particular, they have made the yeast “extraordinarily stable” and thereby suitable for large-scale industrial ethanol production.  This was accomplished by developing a new integration method so that all the cloned genes could be integrated into the yeast chromosomes in high-copy-numbers (for other major improvements on the Purdue Yeast, see www.nancyho.info).  Academic institutes, government laboratories, and ethanol producers including ADM (Archer, Daniels, and Midland Company America – the world’s largest ethanol producer) have tested the Purdue yeast and validated its effectiveness in converting mixtures of glucose and xylose to ethanol from sugars in the crude hydrolysates of various types cellulosic biomass.  Most excitingly, in April 2004, Iogen, a Canadian company, began to use the Purdue yeast to produce ethanol from wheat straw in the world’s first production plant of its kind.  In addition, Iogen has publicly acknowledged that Purdue's recombinant glucose- and xylose-fermenting yeast is the most effective microorganism available for the production of ethanol from cellulosic materials (Purdue News release and ASM News letter, Oct 04, 2004).

Dr. Ho treasures the opportunity to make the Saccharomyces yeast co-ferment glucose and xylose.  That has made it possible to use the safe, effective Saccharomyces yeast to produce ethanol as well as many other useful “green” chemicals from the world’s largest renewable resource – cellulosic biomass.

However, during her 30-year research career in the US, she has been totally dependent on outside public or private funding to sustain her work.  As such, she has felt strongly that the government financial support for applied research, particularly in the last ten years, is neither sufficient nor properly dispersed.  Government funding cannot facilitate the rapid development of technology that is vitally important for the Nation’s wellbeing – such as energy independence and improving the environment.

In this country, numerous important endeavors are carried out by not-for-profit organizations.  Dr. Ho felt that a not-for-profit organization could support the development and distribution of recombinant industrial microorganisms to industry, similar to the role of the ATCC in safeguarding, producing, and distributing microorganisms to scientists for basic and applied studies around the world (www.atcc.org).  This is why Dr. Ho established the Genetic Institute for Fuels and Chemicals (GIFC) a few years ago to shoulder such responsibilities.