Hahn S K, Chang Y K, Lee S Y
BioProcess Engineering Research Center, Korea Advanced Institute of Science and Technology, Taejon.
Appl Environ Microbiol. 1995 Jan;61(1):34-9. doi: 10.1128/aem.61.1.34-39.1995.
We studied recovery of poly(3-hydroxybutyric acid) (PHB) from Alcaligenes eutrophus and a recombinant Escherichia coli strain harboring the A. eutrophus poly(3-hydroxyalkanoic acid) biosynthesis genes. The amount of PHB degraded to a lower-molecular-weight compound in A. eutrophus during the recovery process was significant when sodium hypochlorite was used, but the amount degraded in the recombinant E. coli strain was negligible. However, there was no difference between the two microorganisms in the patterns of molecular weight change when PHB was recovered by using dispersions of a sodium hypochlorite solution and chloroform. To understand these findings, we examined purified PHB and lyophilized cells containing PHB by using a differential scanning calorimeter, a thermogravimetric analyzer, and nuclear magnetic resonance. The results of our analysis of lyophilized whole cells containing PHB with the differential scanning calorimeter suggested that the PHB granules in the recombinant E. coli strain were crystalline, while most of the PHB in A. eutrophus was in a mobile amorphous state. The stability of the native PHB in the recombinant E. coli strain during sodium hypochlorite treatment seemed to be due to its crystalline morphology. In addition, as determined by the thermogravimetric analyzer study, lyophilized cell powder of the recombinant E. coli strain containing PHB exhibited greater thermal stability than purified PHB obtained by chloroform extraction. The PHB preparations extracted from the two microorganisms had identical polymer properties.
我们研究了从真养产碱杆菌以及携带真养产碱杆菌聚（3-羟基链烷酸）生物合成基因的重组大肠杆菌菌株中回收聚（3-羟基丁酸）（PHB）的方法。在回收过程中，当使用次氯酸钠时，真养产碱杆菌中降解为低分子量化合物的PHB量显著，但在重组大肠杆菌菌株中降解的量可忽略不计。然而，当使用次氯酸钠溶液和氯仿的分散液回收PHB时，两种微生物在分子量变化模式上没有差异。为了解这些发现，我们使用差示扫描量热仪、热重分析仪和核磁共振对纯化的PHB和含有PHB的冻干细胞进行了检测。我们用差示扫描量热仪对含有PHB的冻干全细胞进行分析的结果表明，重组大肠杆菌菌株中的PHB颗粒是结晶态的，而真养产碱杆菌中的大部分PHB处于流动无定形态。重组大肠杆菌菌株中天然PHB在次氯酸钠处理过程中的稳定性似乎归因于其结晶形态。此外，通过热重分析仪研究确定，含有PHB的重组大肠杆菌菌株的冻干细胞粉末比通过氯仿萃取获得的纯化PHB表现出更高的热稳定性。从这两种微生物中提取的PHB制剂具有相同的聚合物特性。
