Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2004
Publication Date: 10/11/2004
Citation: Solaiman, D., Ashby, R.D., Foglia, T.A., Marmer, W.N., Kaplan, D.L. 2004. Biosurfactants from microbial fermentation of renewable substrates [abstract]. Industrial Application of Renewable Resources - A Conference on Sustainable Technologies, American Oil Chemists' Society. p. 14.
Technical Abstract: Many microorganisms produce secondary metabolites that have surface-active properties. These compounds not only are useful biosurfactants and bioemulsifiers, but are also indicated as antibiotic and bio-control agents. The majority of microbial surfactants are glycolipids, lipopeptides or lipoproteins, and polymeric compounds. Among the most studied biosurfactants are sophorolipids, rhamnolipids, and emulsan. Sophorolipids (SL), produced by several yeast species, are composed of sophorose disaccharide glycosidically linked to a hydroxy fatty acid. A high-level production of SLs (up to 400 g SL/liter culture) by Candida bombicola yeast requires the co-feeding of carbohydrate and lipid feedstocks. The lipid substrate governs the chain length and the number of double bonds of the fatty acid moiety. The type of substrate also affects the proportion of the lactonic and free acid forms of the C. bombicola SLs. Aqueous solutions of various SLs have minimal surface tension values of 30-35 mN/m. Rhamnolipids (RL), produced by the bacterium Pseudomonas aeruginosa, contain mono- or di-rhamnose and a beta-hydroxyalkanoyl-beta-hydroxyalkanoic acid (usually of C10 or C12 chain-length) as their hydrophilic and hydrophobic moieties, respectively. Production of RLs from renewable feedstocks including fats and oils has been demonstrated, and volumetric yields of 7-100 g RL/l culture were claimed. Aqueous solutions of RLs exhibit a minimum surface tension value of 29 mN/m. Emulsan is a polymeric biosurfactant produced by Acinetobacter calcoaceticus. It contains a heteropolysaccharide backbone with acyl groups attached through O- and N-acyl linkages. Structurally varied renewable feedstocks were shown to influence the chemical compositions and thus the emulsification properties of emulsans. This presentation will survey the use of various renewable materials to address the need of lowering the production costs and improving the properties of these biosurfactants.