"Biocatalytic Routes to Bio-based Chemicals"

Richard A. Gross
NSF I/UCRC for Biocatalysis and Bioprocessing of Macromolecules, Department of Chemical
and Biological Sciences; Polytechnic University, Six Metrotech Center,
Brooklyn, NY 11201 http://www.poly.edu/grossbiocat/

New and versatile biocatalytic methods were developed that offer mild and efficient options for prepolymer and polymer synthesis. Lipase B from Candida antartica (CALB), physically immobilized on hydrophobic macroporous resins, is a remarkable catalyst for both ring-opening and step-condensation reactions. A new family of aliphatic polyolpolyesters and polycarbonates was discovered using sugar alcohol building blocks such as glycerol and sorbitol. Lipase regioselectivity enables direct copolymerizations of polyols with a range of diols and diacids to give non-crosslinked high molecular weight materials with controlled branching. The mild reaction conditions (50 to 90 oC) allow incorporation of chemically and/or thermally sensitive co-monomers such as silicones. For example, silicones directly linked to carbohydrates (“sweet silicones”) were prepared that have interesting surfactant properties.
Fatty acids are important components to surfactants and many other chemicals of industrial importance. Our laboratory has developed new methods to prepare ricinoleic acid analogs by fermentation utilizing microorganisms. Purified analogs can be used as building blocks or components in many products, or converted into oligomers and polymers. Fatty acids were transformed by an engineered Candida tropicalis strain, to their corresponding a,?-dicarboxylic acids, a-carboxyl-?-hydroxyl fatty acids, or a mixture of these products. Moreover, a wide range of a,?-dicarboxylic acids with different carbon length (C12-C22) and internal functionality were prepared due to the biocatalysts ability to accept a wide range of fatty acid substrates.
Work to develop natural and modified sophorolipid analogs for cosmetic and medicinal applications will be described. Sophorolipids are extracellular glycolipids produced mainly by Candida species when grown on carbohydrates or fatty acids or their mixtures. Typically, sophorolipids consist of a dimeric sophorose linked by a glycosidic bond to the penultimate hydroxyl group of an 18-carbon fatty acid. Work by us has shown that by specific modification of sophorolipids, compounds were obtained that show promise as therapeutic agents: spermicidal and virucidal properties (Gross et al. 2004), immunomodulators for treatment of antiendotoxic (septic) shock by cytokine downregulation (Kandil et al. 2003), and anti-cancer activity (Scholz et al., 1998; Gross et al., 1999). Sophorolipids also may be used as active components in formulations for enhanced oil recovery, cosmetics, germicidal preparations and in detergents (Singh et al. 2003 and references therein).
References :
Kulshrestha, A. S.; Gao, W.; Gross, R.A. “Glycerol Copolyesters: Control of Branching and Molecular Weight
Using a Lipase Catalyst”, Macromolecules, (2005); 38(8); 3193-3204
Zhang, L., Somasundaran, P., Singh, S. K., Felse, A. P., Gross, R.A. Synthesis and interfacial properties of
sophorolipid derivatives Colloids and Surfaces A: Physicochem.Eng. Aspects; 240; 75-82 (2004) Sahoo, B.; Brandstadt, K. F.; Lane, T. H.; Gross, R. A. “Sweet Silicones": Biocatalytic Reactions to Form
Organosilicon Carbohydrate Macromers Org. Lett.; 7(18); 3857-3860 (2005).
V Guilmanov, A Ballistreri, G Impallomeni, R.A. Gross, “Oxygen Transfer Rate and Sophorose Lipid Production by
Candida bombicola”, Biotechnol. and Bioeng; 77(5), 489-494 (2002)
Keywords : Lipids, biosurfactants, polyol-polyesters, lipase-catalysis, silicones

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