The sequence structures of bacterially synthesized copoly(3-hydroxyalkanoates), isolated from the sludge developed in the anaerobic–aerobic waste-water treatment process containing propionate as a carbon source, were analysed by 13C NMR spectroscopy. These copolyesters were composed of four different monomer units, 3-hydroxybutyrate, 3-hydroxyvalerate, 3-hydroxy-2-methylbutyrate and 3-hydroxy-2-methylvalerate. By using water/acetone mixed solvent, one of the copolyester samples was fractionated into fractions by differences in average molecular weights as well as in monomer compositions. The carbonyl carbon resonances, split due to differences in diad sequences, were analysed on the basis of Bernoullian statistics. It is suggested that these copolyesters were mixtures of random copolymers with different monomer compositions.
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Inoue et al. (1996) studied this question.