|Price and cost comparison for sugar- and fatty acid-based feedstocks in the production of biofuels and biochemicals. (a) Prices of raw sugar, palm fatty acid distillate (PFAD) and non-edible tallow on a per-pound of carbon. (b) Feedstock cost per gallon of ethanol produced. Source: Dellomonaco 2010, Supplementary material I. Click to enlarge.|
Glycos Biotechnologies, Inc., an emerging biochemical company leveraging metabolic and microbial engineering (earlier post), has developed what it says is the first microbial platform for the efficient synthesis of biofuels and biochemicals from fatty acids. The research was done in collaboration with GlycosBio’s Scientific Advisory Board Chairman Prof. Ramon Gonzalez and his group at Rice University. The results were recently published in the journal Applied and Environmental Microbiology.
While cellulosic sugars from edible crops (e.g., corn) have been used as the primary feedstock in the biological production of renewable fuels and chemicals, concern over the sustainability has caused the industry to look for alternative feedstock sources. While nonedible lignocellulosic sugars have been proposed as a primary feedstock, the availability of fatty acid (FA)-rich feedstocks and recent progress in the development of oil-accumulating organisms make FAs an attractive alternative.
In addition to their abundance, the metabolism of FAs is very efficient and could support product yields significantly higher than those obtained from lignocellulosic sugars.
However, FAs are metabolized only under respiratory conditions, a metabolic mode that does not support the synthesis of fermentation products. In the work reported here we engineered several native and heterologous fermentative pathways to function in Escherichia coli under aerobic conditions, thus creating a respiro-fermentative metabolic mode that enables the efficient synthesis of fuels and chemicals from FAs.—Dellomonaco et al.
The researchers metabolically engineered native and heterologous fermentative pathways to function in E. coli under aerobic conditions. This process created the industry’s first respiro-fermentative metabolic mode for the efficient catabolism of fatty acids and the synthesis of fuels and chemicals in E. coli.
Based on this discovery, the team of researchers was able to successfully synthesize biofuels including ethanol and butanol, and biochemicals including acetate, acetone, isopropanol, succinate and propionate from fatty acids. Like ethanol, all of these chemicals show excellent yield advantages over the comparable sugar-based fermentation processes:
The yields of ethanol, acetate, and acetone in the engineered strains exceeded those reported in the literature for their production from sugars, and in the cases of ethanol and acetate they also surpassed the maximum theoretical values that can be achieved from lignocellulosic sugars.
Butanol was produced at yields and titers that were between 2- and 3-fold higher than those reported for its production from sugars in previously engineered microorganisms.
Until now, microbial platforms to enable the biological production of fuels and chemicals from fatty acids have been nearly non-existent. Through our research, we were able to prove the effectiveness of fatty acids to produce higher value chemicals and at very high yields with an empirical ethanol yield double that which is usually achieved with sugars. These results demonstrate that fatty acids can be a great alternative to cellulosic sugars.—Paul Campbell, Ph.D., Chief Science Officer for Glycos Biotechnologies
At GlycosBio, we’ve been able to uniquely optimize the biochemical production of fuels and chemicals from microbial strains enabling a very flexible platform that can support a wide range of industrial and agricultural feedstocks. Edible oil-rich crops such as rapeseed, sunflower, soybean, and palm are widely available and non-edible fatty acid-rich crops along with industrial by-products are receiving more attention as longer-term alternatives. With this research complete, the industry can begin to realize the advantage of and choose a fatty acid approach to biofuel and biochemical production. For GlycosBio, this research further supports our ability and opportunity to work with oleochemical and biodiesel producers who generate glycerol and fatty acid wastes.—Walter Burnap, President and Chief Financial Officer for Glycos Biotechnologies
Clementina Dellomonaco, Carlos Rivera, Paul Campbell, and Ramon Gonzalez (2010) Engineered Respiro-Fermentative Metabolism for the Production of Biofuels and Biochemicals from Fatty Acid-Rich Feedstocks. Applied and Environmental Microbiology p. 5067-5078, Vol. 76, No. 15 doi: 10.1128/AEM.00046-10