Sun Zhiyong, Ramsay Juliana A, Guay Martin, Ramsay Bruce A
Chemical Engineering, Queen's University, Kingston, Ontario, Canada.
Appl Microbiol Biotechnol. 2009 Mar;82(4):657-62. doi: 10.1007/s00253-008-1785-7. Epub 2008 Dec 3.
Unsaturated medium-chain-length polyhydroxyalkanoates (MCL-PHA) were produced at a productivity of 0.63-1.09 g PHA l(-1) h(-1) with final PHA content ranging from 42.6 to 55.8% in single-stage, carbon-limited, fed-batch fermentations of Pseudomonas putida KT2440. A mixture of nonanoic acid (NA) and 10-undecenoic acid (UDA=) was fed exponentially to control growth rate. Varying the specific growth rate (0.14 h(-1) vs. 0.23 h(-1)) at similar substrate feed ratios (NA:UDA= = 5:1) had little effect on the final PHA content and relative composition. However, decreasing the NA:UDA= ratio decreased the final amount of PHA produced from 56% with NA:UDA= = 5.07:1 to only 42% at NA:UDA= = 2.47:1. The molar fraction of all 3-hydroxyalkanoate monomers in the PHA product was relatively constant throughout each fermentation, indicating that the final product was homogeneous rather than a mixture of different copolymers. A linear relationship between unsaturation of the PHA produced and unsaturation of the carbon feed was found, which demonstrates the feasibility of producing unsaturated MCL-PHAs with controlled polymeric composition in a fed-batch process.
在以恶臭假单胞菌KT2440进行的单阶段、碳限制补料分批发酵中，不饱和中链长度聚羟基脂肪酸酯（MCL-PHA）的生产效率为0.63 - 1.09 g PHA l⁻¹ h⁻¹，最终PHA含量在42.6%至55.8%之间。将壬酸（NA）和10-十一碳烯酸（UDA=）的混合物指数补料以控制生长速率。在相似的底物补料比（NA:UDA= = 5:1）下改变比生长速率（0.14 h⁻¹对0.23 h⁻¹）对最终PHA含量和相对组成影响不大。然而，降低NA:UDA=比例会使PHA的最终产量从NA:UDA= = 5.07:1时的56%降至NA:UDA= = 2.47:1时的仅42%。在每个发酵过程中，PHA产物中所有3-羟基脂肪酸酯单体的摩尔分数相对恒定，表明最终产物是均匀的，而非不同共聚物的混合物。发现所生产的PHA的不饱和度与碳源进料的不饱和度之间存在线性关系，这证明了在补料分批过程中生产具有可控聚合物组成的不饱和MCL-PHAs的可行性。
