Copolyesters of 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB) with a wide range of compositions from 0 to 100 mol % 4HB were microbially synthesized at 30 °C by Alcaligenes eutrophus from 4-hydroxybutyric acid in the presence of some additives. When 4-hydroxybutyric acid, citrate, and ammonium sulfate were fed as mixed substrates in the aqueous culture of A. eutrophus, P(3HB-co-4HB) copolymers with compositions of 70-100 mol % 4HB were produced. The structure and physical properties of P(3HB-co-4HB) copolymers were characterized by and 13C NMR spectroscopy, X-ray diffraction, gel-permeation chromatography, differential scanning calorimetry, tensile test, and dynamic mechanical spectroscopy. In addition, the effects of 4HB units on the rate of enzymatic degradation of P(3HB-co-4HB) films were studied in the aqueous solution of an extracellular P(3HB) depolymerase from A. faecalis.

Abstract-Wave-propagation equations, including effectively the second derivative in time under the condition of a small difference between the group and phase velocities and the first derivative in position in the group velocity coordinate, are derived based on the slowly evolving wave approximation. These can describe ultrabroadband optical pulse propagation with not only self-phase modulation (SPM), but also induced-phase modulation (IPM) in the monocycle regime in a fiber. It is shown that linear dispersion effects can be rigorously included in the numerical calculations. Calculations including SPM in a single-mode fused-silica fiber with the Raman effect are performed and compared with experimental results. Also, calculations including IPM in the fused-silica fiber are compared with experimental results. The effects of each term in the calculations on spectra are analyzed and it is shown that inclusion of the Raman effect and the dispersion of the effective core area is important for obtaining better agreement with experiments. It is shown that inclusion of more than third-order dispersion terms is necessary for calculations of monocycle pulse propagation.Index Terms-Nonlinear fiber optics, ultrabroadband and monocycle pulse propagation, self-and induced-phase modulation.