Microbial synthesis of new poly(a-hydroxyalkanoates) bearing phenyl groups: preparation and characterization

ABRAHAM,G.A.; GALLARDO,A.; SAN ROMAN,J; OLIVERA, E.R.; JODRA,R.; GARCIA,B.; MIÑAMBRES,B.; GARCIA,J.L.; LUENGO,J.M.

BIOMACROMOLECULES

American Chemical Society Publications

Lugar: Washington DC, USA; Año: 2001 vol. 2 p. 562 - 567

1525-7797

New poly(b-hydroxyalkanoates) having aromatics groups (so called PHPhAs) from a microbial origin have been characterized. These polymers are produced and accumulated as reserve materials when a b-oxidation mutant of Pseudomonas putida U, disrupted in the gene that encodes the 3-keto-acyl-CoA thiolase (fadA), was cultured in a chemically defined medium containing different aromatic fatty acids (6-phenylhexanoic acid, 7-phenylheptanoic acid, a mixture of them, or 8-phenyloctanoic acid) as carbon sources. The polymers were extracted from the bacteria, purified and characterized by using 13C nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). Structural studies revealed that when 6-phenylhexanoic acid was added to the cultures, an homopolymer (poly-3-hydroxy-6-phenylhexanoate) was accumulated. The feeding with 8-phenyloctanoic acid and 7-phenylheptanoic acid leads to the formation of copolymers of the corresponding units with the n-2 carbons formed after deacetylation, copoly(3-hydroxy-8-phenyloctanoate)-(3-hydroxy-6-phenylhexanoate) and copoly(3-hydroxy-7-phenylheptanoate)-(3-hydroxy-5-phenylvalerate), respectively. The mixture of 6-phenylhexanoic acid 7-phenylheptanoic acid gave rise to the corresponding terpolymer, copoly(3-hydroxy-7-phenylheptanoate)-(3-hydroxy-6-phenylhexanoate)-(3-hydroxy-5-phenylvalerate). Studies on the chemical structure of these three polyesters revealed that they are true copolymers but not a mixture of homopolymers, and that the different monomeric units are randomly incorporated in the macromolecular chains. Thermal behavior and molecular weight distribution were also discussed. These compounds have a dual attractive interest in function of: (i) their broad use as biodegradable polymers, and (ii) their possible biomedical applications.