New Microorganisms for Ethanol Production: An Overview

Saccharomyces cerevisiae is the mainstay microorganism for converting a variety of glucose feedstreams to ethanol. This yeast is easy to work with, reliable, robust, highly productive, and safe. It is well characterized from a genetic and biochemical perspective. The only serious shortcoming of Saccharomyces is its inability to ferment some of the pentose sugars found in many feedstocks. Thisdeficiency is particularly acute in a very marginal process or when the price of a given feedstock rises substantially and it is necessary to convert all of the carbonhydrate portion to fermentable sugars. With the advent of genetic engineering, primarily over the past 10 years, it is now possible to greatly expand the metabolic capabilities of given microorganism. Recently, a number of novelbacterial and yeast strains have been created with enhanced genetic properties. Some of the biochemical attributes of these new strains make them potential candidates to replace the well-entrenched Saccharomyces cerevisiae as the standard-bearer in the ethanol industry. The scientific developments as well as the possible economic ramifications will be discussed.