Preparation of a bacterial polyester with carboxy groups in side chains

Unsaturated biopolyesters were produced by Pseudomonas oleovorans from two mixtures of sodium octanoate and 10-undecenoic acid (90:10 and 80:20 mol/mol) as a reserve of carbon and energy. Chemical modification of double bonds into carboxyl groups was carried out with potassium permanganate (KMnO₄). Oxidation reaction was proved by ¹H and ¹³C NMR spectroscopy. Molecular weights of modified biopolyesters were not highly affected by the oxidation reaction. Hydrophilicity was enhanced; polyester containing 25 % of repeating units pendant carboxylic acid end groups was soluble in polar solvents such as methanol, dimethylsulfoxide or a 85:15 (v/v) acetone/water mixture. Moreover, the presence of carboxy pendant groups was important with respect to the hydrolytic degradation. A fast hydrolysis was observed at pH = 11 in 24 hours for the carboxylated modified polyester containing 25 % of carboxyl groups.