title: Mild, solvent-free omega-hydroxy acid polycondensations catalyzed by candida antarctica lipase B.
abstract: Immobilized Candida antarctica Lipase B (Novozyme-435) was studied for bulk polyesterifications of linear aliphatic hydroxyacids of variable chain length. The products formed were not fractionated by precipitation. The relative reactivity of the hydroxyacids was l6-hydroxyhexadecanoic acid approximately 12-hydroxydodecanoic acid approximately 10-hydroxydecanoic acid (DPavg congruent with 120, Mw/Mn <or = 1.5, 48 h, 90 degrees C) > 6-hydroxyhexanoic acid (DPavg congruent with 80, Mw/Mn < or = 1.5, 48 h, 90 degrees C). Remarkable improvements in molecular-weight buildup resulted from leaving water in the reaction. By 4 h, without application of vacuum, the DPavg for 12- and 16-carbon hydroxyacids was about 90. In contrast, with identical substrates and water removal, the DPavg at 4 h was about 23. Large differences in the molecular-weight build up of 12-hydroxydodecanoic acid were observed for catalyst concentrations (%-by-wt relative to monomer) of 0.1, 0.5, 1, and 10. Nevertheless, by 24 h, with 1% catalyst containing 0.1% lipase, poly(12-hydroxydodecanoic acid) with Mn 17 600 was formed. For 12-hydroxydodecanoic acid polymerization at 90 degrees C, the catalyst activity decreased by 7, 18, and 25% at reaction times of 4, 24, and 48 h, respectively. Furthermore, the retention of catalyst activity was invariable as a function of the substrates used.
authors.affiliation: NSF I/UCR Center for Biocatalysis and Bioprocessing of Macromolecules, Polytechnic University, Brooklyn, New York 11201, USA.
authors.forename: Anil
authors.initials: A
authors.lastname: Mahapatro
authors.forename: Ajay
authors.initials: A
authors.lastname: Kumar
authors.forename: Richard A
authors.initials: RA
authors.lastname: Gross
mesh_terms: D002175:Candida / Q000201:enzymology*; D002384:Catalysis; D004800:Enzymes, Immobilized / Q000378:metabolism; D005656:Fungal Proteins; D006880:Hydroxy Acids / Q000378:metabolism*; D008049:Lipase / Q000378:metabolism*; D008970:Molecular Weight; D011091:Polyesters / Q000138:chemical synthesis* / Q000378:metabolism; D013379:Substrate Specificity; D014867:Water
chemical_list: D004800:Enzymes, Immobilized; D005656:Fungal Proteins; D006880:Hydroxy Acids; D011091:Polyesters; D014867:Water; D008049:Lipase; C431349:lipase B, Candida antarctica