To date most effort, for good reason has gone into simply unraveling cellulose into constituent sugars and lignin. As these are freeing up, it then becomes necessary to process the derivative products. We have already reported on work on lignin and this is one of the resulting sugars from the processing of cellulose..
It does look as if we will establish protocols and pathways to convert cellulose into a desirable biofuel. The magic question then becomes whether we can do it profitably.
The multiple processes and separation steps are somewhat discouraging, particularly when you will also have to fine tune the feedstock. However, uniform feedstocks such as corn stover and cattail waste and bagasse are all excellent sources of renewable feedstocks.
Researcher discovers enzyme to ferment xylose
By Anna Austin
Web exclusive posted Feb. 17, 2009, at 3:45 p.m. CST
Eckhard Boels, cofounder of Swiss biofuel company Butalco gmbH and a professor at Goethe-University in Frankfurt, Germany, has discovered a new enzyme which teaches yeast cells to ferment xylose into ethanol. Xylose is an unused waste sugar in the cellulosic ethanol production process.
According to Boles, one of the major problems with cellulosic ethanol is that when utilizing other parts of plants, which today are considered waste, yeasts are unable to ferment some of the sugars in a majority of the plant material.
Saccharomyces cerevisiae (SC), a yeast commonly used for ethanol production, lacks the ability to ferment some sugars. “Heterologous expression of a xylose isomerase would enable yeast cells to metabolize xylose,” Boles said. “However, many attempts to express a prokaryotic xylose isomerase with high activity in SC have failed so far. We have screened nucleic acid databases for sequences encoding putative xylose isomerases, and finally could clone and successfully express a highly active new kind of xylose isomerase from an anaerobic bacterium in SC.”
The new enzyme was taken from the bacterial organism and inserted into yeast cells that were retrieved from a commercial ethanol plant. “With just a minor effort, we were able to teach the yeast cells how to ferment the xylose into ethanol,” Boles said.
Boles believe the findings may provide an excellent starting point for further improvement of xylose fermentation in industrial yeast strains, and greatly enhance the development of an efficient biomass-to-ethanol fermentation process. His company, Butalco gmbH, is now working to construct yeast strains to convert plant waste materials into biobutanol.
The research was published in the Applied and Environmental Microbiology journal in February.