Serafim Luísa S, Lemos Paulo C, Torres Cristiana, Reis Maria A M, Ramos Ana M
REQUIMTE/CQFB, Chemistry Department, FCT/Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
Macromol Biosci. 2008 Apr 9;8(4):355-66. doi: 10.1002/mabi.200700200.
The characterization of polyhydroxyalkanoates (PHA) produced by mixed cultures is fundamental for foreseeing the possible final applications of the polymer. In this study PHA produced under aerobic dynamic feeding (ADF) conditions are characterized. The PHA produced shows a stable average molecular weight ([symbol: see text]) in the range (1.0-3.0) x 10(6), along three years of reactor operation. Attempts to improve the amount of PHA produced did not introduce significant variations on the values [symbol: see text]. Along this period, the polydispersity indices (PDI) were between 1.3 and 2.2. The use of different carbon sources allowed the tailoring of polymer composition: homopolymers of poly(3-hydroxybutyrate), P(3HB), were obtained with acetate and butyrate, whereas a mixture of acetate and propionate, and propionate and valerate, gave terpolymers of 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), and 2-methyl-3-hydroxyvalerate (2M3HV). All of these PHA had [symbol: see text] between 2.0 x 10(6) and 3.0 x 10(6). Thermal characterization of the produced polymers showed values of glass transition temperature, melting temperature, melting enthalpy, and crystallinity slightly lower than those obtained for PHA from pure cultures. The introduction of a purification step during the polymer extraction process allowed the elimination of possible contaminants but did not significantly improve the polymer quality.
混合培养物产生的聚羟基脂肪酸酯（PHA）的特性对于预见该聚合物可能的最终应用至关重要。在本研究中，对在好氧动态进料（ADF）条件下产生的PHA进行了表征。在三年的反应器运行过程中，所产生的PHA显示出稳定的平均分子量（[符号：见原文]），范围为(1.0 - 3.0)×10⁶ 。提高PHA产量的尝试并未使[符号：见原文]值产生显著变化。在此期间，多分散指数（PDI）在1.3至2.2之间。使用不同的碳源可定制聚合物组成：用乙酸盐和丁酸盐可获得聚（3 - 羟基丁酸酯）P(3HB)的均聚物，而乙酸盐和丙酸盐以及丙酸盐和戊酸盐的混合物则产生3 - 羟基丁酸酯（3HB）、3 - 羟基戊酸酯（3HV）和2 - 甲基 - 3 - 羟基戊酸酯（2M3HV）的三元共聚物。所有这些PHA的[符号：见原文]在2.0×10⁶至3.0×10⁶之间。所生产聚合物的热表征显示，其玻璃化转变温度、熔点、熔化焓和结晶度的值略低于纯培养物中PHA的相应值。在聚合物提取过程中引入纯化步骤可消除可能的污染物，但并未显著提高聚合物质量。
