USA – bacteria transform by-product into biofuel

With US biodiesel production at an all-time high and a record number of new biodiesel plants under construction, the industry is facing an impending crisis over waste glycerine, the major by-product of biodiesel production.



Environmentalresearchweb.org reports that researchers from Rice University, US, believe they have found an answer to this problem – a bacterium that ferments glycerine and produces ethanol, another popular biofuel.



"We identified the metabolic processes and conditions that allow a known strain of E. coli to convert glycerine into ethanol," said chemical engineer Ramon Gonzalez. "It‘‘s also very efficient. We estimate the operational costs to be about 40% less that those of producing ethanol from corn."



Gonzalez says the biodiesel industry‘‘s rapid growth has created a glycerine glut. The glut has forced glycerine producers like Dow Chemical and Procter and Gamble to shutter plants, and some biodiesel producers are already unable to sell glycerine and instead must pay to dispose of it.



"One pound of glycerine is produced for every 10 pounds of biodiesel," said Gonzalez. "The biodiesel business has tight margins, and until recently, glycerine was a valuable commodity, one that producers counted on selling to ensure profitability."



Researchers across the globe are racing to find ways to turn waste glycerine into profit. While some are looking at traditional chemical processing – finding a way to catalyse reactions that break glycerine into other chemicals – others, including Gonzalez, are focused on biological conversion.



In biological conversion, researchers engineer a microorganism that can eat a specific chemical feedstock and excrete something useful. Many drugs are made this way, and the chemical processing industry is increasingly finding bioprocessing to be a "greener", and sometimes cheaper, alternative to chemical processing.



"We did not discover a new strain of bacterium but rather the environmental conditions that enable a very well known microorganism to conduct a metabolic process it was thought unable to perform," says Gonzalez.



Very few microorganisms are capable of digesting glycerine in an oxygen-free environment. This oxygen-free process – known as anaerobic fermentation – is the most economical and widely used process for biological conversion. The microorganism used by the Rice researchers is not affected by oxygen, but if the target product is a fuel, it is convenient to have an environment with few or no electron acceptors because they will take the electrons/energy you want to put in your fuel.



"We are confident that our findings will enable the use of E. coli to produce anaerobically ethanol and other products from glycerine with higher yields and lower costs than can be obtained using common sugar-based feedstocks like glucose and xylose," Gonzalez said. "Our process takes around the same time as current yeast fermentations that produce ethanol from corn- or sugar cane-derived sugars."



A significant advantage of the technology is that employing glycerine eliminates all the equipment typically needed in a facility that uses sugars (i. e. the kit needed to extract the sugars from corn, sugar cane or, in the future, cellulosic biomass). This translates into lower capital and operational costs.



The work is being patented and the researchers are planning to see this process used at a commercial scale. About the author



Nadya Anscombe is a contributing editor to environmentalresearchweb.