Xylose Enzyme Discovered

Step by step we are finding ways to convert cellulose into a usable biofuel like ethanol. This company is also attempting to produce a better biofuel that ethanol itself. Their present focus is on biobutanol.

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

http://www.ethanolproducer.com/article.jsp?article_id=5390

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.

Methane and pottery

In the end concerns over methane production are irrelevant. We have doubled production in the last century and it is all gone. The reason is ultimately very simple. It migrates to the upper atmosphere and is consumed. This is something that is not an option for CO2.

Does the sharp increase in methane reaching the troposphere have any effect whatsoever? The quick answer is nothing that is obvious. It is a little like measuring the effect of the Mississippi on the Atlantic. The practical answer as always is to make as much as you desire and see were it takes you. My guess is nowhere.

That means that methane production concerns regarding all forms of biowaste combustion are misplaced. My real concern would be for well intentioned government regulation been actively imposed forcing a larger industrial price for the use of the method.

The second issue that has attracted comment is the association of pottery shards in the terra preta soils. I naturally postulated that this was partly to do with the disposal of kitchen waste in the corn stover stack kilns as we described in earlier postings in July. I also realized that a large bowl would have to be used to transport hot coals to the top of the stack and perhaps dumped into a prepared chimney.

These bowls are as primitive as you can get and very prone to heat breakage, so the presence of pottery is no surprise. My discomfort came from the fact that they would have normally taken broken pottery away with them for disposal elsewhere. So why not?

The answer came to me this morning. It is natural to take the bowl of coals to the top of the stack and to dump them there in the center and to let the coals slowly burn out a chimney. The problem is that you have to cover these coals with dirt to prevent flame out. The best way to do that is to upend the bowl on top of the coals and to throw dirt on top of that. Otherwise, the coals will end up been smothered by the dirt. The bowl would then migrate slowly to the bottom of the stack. In the process the high heat would cause this low quality pottery to breakup into very small pieces not worth recovering or causing any difficulty for cultivation.

Actually a pretty nifty solution to the problem of controlling the ignition coal mass. While this was progressing, the farmer would stand by to throw dirt on any emerging openings in the stack to prevent a flare up.