Table_1_The Thermal and Mechanical Properties of Medium Chain-Length Polyhydroxyalkanoates Produced by Pseudomonas putida LS46 on Various Substrates.DOCX

Medium chain-length polyhydroxyalkanoates (mcl-PHA) were produced by Pseudomonas putida LS46 cultured with a variety of carbohydrate and fatty acid substrates. The monomer compositions and molecular weights of the polymers varied greatly and was dependent on whether the substrate was metabolized via the fatty acid degradation or the de novo fatty acid synthesis pathways. The highest molecular weights were obtained from medium chain-length fatty acids, whereas low molecular weights were obtained from longer chain-length and more unsaturated fatty acids or carbohydrates. The differences in monomer compositions and molecular weights due to the choice of substrate did not affect the polymer thermal degradation point. The glass transition temperatures varied from −39.4°C to −52.7°C. The melting points, when observed, ranged from 43.2°C to 51.2°C. However, a profound substrate effect was observed on the crystallinity of these polymers. Reduced crystallinity was observed when the monomer compositions deviated away from C8–C10 monomer lengths. The highest crystallinity was observed from medium chain-length fatty acids, which resulted in polymers with the highest tensile strength. The polymer produced from octanoic acid exhibited the highest tensile strength of 4.3 MPa with an elongation-at-break of 162%, whereas the polymers produced from unsaturated, long-chain fatty acids remained amorphous. A comparative analysis of the substrate effect on the physical-mechanical and thermal properties of mcl-PHAs better clarifies the relationship between the monomer composition and their potential applications, and also aids to direct future PHA synthesis research toward properties of interest.

通过假单胞菌属细菌 Pseudomonas putida LS46 在多种碳水化合物和脂肪酸底物上的培养，产生了中链长度的多羟基脂肪族聚酯（mcl-PHA）。这些聚合物的单体组成和分子量差异显著，且其变化取决于底物是通过脂肪酸降解途径还是通过从头合成脂肪酸途径进行代谢。分子量最高的是来自中链长度的脂肪酸，而低分子量则来自长链和更高不饱和度的脂肪酸或碳水化合物。底物选择导致的单体组成和分子量的差异并未影响聚合物的热降解点。玻璃化转变温度范围在 -39.4°C 至 -52.7°C 之间。观察到的熔点范围为 43.2°C 至 51.2°C。然而，底物对聚合物结晶度的影响显著。当单体组成偏离 C8–C10 单体长度时，观察到结晶度降低。来自中链长度脂肪酸的聚合物表现出最高的结晶度，从而导致了具有最高拉伸强度的聚合物。由辛酸产生的聚合物展现了最高的拉伸强度，达到 4.3 MPa，断裂伸长率为 162%，而来自不饱和、长链脂肪酸的聚合物则保持非晶态。对底物对 mcl-PHAs 的物理机械性能和热性能的比较分析，进一步阐明了单体组成与其潜在应用之间的关系，并有助于指导未来的 PHA 合成研究，使其向感兴趣的特性方向发展。