ARS | Publication request: Using Fermentation to Ease the Glycerol Conundrum

Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: February 21, 2007
Publication Date: May 13, 2007
Citation: Ashby, R.D., Solaiman, D., Foglia, T.A. 2007. Using Fermentation to Ease the Glycerol Conundrum [abstract]. Annual Meeting and Expo of the American Oil Chemists' Society. p. 100.

Technical Abstract: The demand for alternative fuels is becoming more pronounced as the cost of petroleum rises. Biodiesel, a renewable fuel derived from oils and fats, is quickly being established as a safe, dependable option in many applications where petroleum has traditionally been used. However, the rapid growth in the biodiesel industry has resulted in large glycerol stocks whose increased availability lowers value and negatively impacts biodiesel economics. As a result, new outlets for glycerol are critical to help offset biodiesel production costs. One promising option is to use glycerol as a fermentation feedstock for the microbial production of "value-added" materials. We are addressing the fermentation-based synthesis of microbial polyesters (e.g, polyhydroxyalkanoates, PHA), polyamides (e.g, gamma-polyglutamic acid, gamma-PGA) and glycolipid surfactants (e.g, sophorolipids, SL) from both refined and crude glycerol. To date, it has been determined that both poly-3-hydroxybutyrate (PHB, a semi-crystalline thermoplastic polymer) and medium-chain-length poly-3-hydroxyalkanoates (mcl-PHA, an amorphous elastomeric polymer) can be produced from glycerol by different strains of Pseudomonas and that gamma-PGA (a water soluble polymer) is produced by Bacillus licheniformis using glycerol as a key media ingredient. Lastly, the yeast, Candida bombicola, was shown to utilize both refined and crude glycerol in the synthesis of SLs. Generally, the preferred structural conformation of SL is as a diacetylated lactone with either a C16 or C18 hydroxy fatty acid moiety attached at the omega-1 or omega carbon. Refined glycerol resulted in SL that was 99% in the lactone form. However, the use of crude biodiesel glycerol increased the open-chain SL content to 60%, which impacted the surface active properties of the SL by increasing the minimum surface tension and critical micelle concentration. By broadening the collection of possible glycerol-based bio-products it will be possible to use fermentation as an additional outlet for the biodiesel coproduct stream and at the same time control production costs.