Kenny Shane T, Runic Jasmina Nikodinovic, Kaminsky Walter, Woods Trevor, Babu Ramesh P, Keely Chris M, Blau Werner, O'Connor Kevin E
School of Biomolecular and Biomedical Sciences, Centre for Synthesis and Chemical Biology, National University of Ireland, University College Dublin, Belfield, Dublin 4, Republic of Ireland.
Environ Sci Technol. 2008 Oct 15;42(20):7696-701. doi: 10.1021/es801010e.
The conversion of the petrochemical polymer polyethylene terephthalate (PET) to a biodegradable plastic polyhydroxyal-kanoate (PHA) is described here. PET was pyrolised at 450 degrees C resulting in the production of a solid, liquid, and gaseous fraction. The liquid and gaseous fractions were burnt for energy recovery, whereas the solid fraction terephthalic acid (TA) was used as the feedstock for bacterial production of PHA. Strains previously reported to grow on TA were unable to accumulate PHA. We therefore isolated bacteria from soil exposed to PET granules at a PET bottle processing plant From the 32 strains isolated, three strains capable of accumulation of medium chain length PHA (mclPHA) from TA as a sole source of carbon and energy were selected for further study. These isolates were identified using 16S rDNA techniques as P. putida (GO16), P. putida (GO19), and P. frederiksbergensis (GO23). P. putida GO16 and GO19 accumulate PHA composed predominantly of a 3-hydroxydecanoic acid monomer while P. frederiksbergensis GO23 accumulates 3-hydroxydecanoic acid as the predominant monomer with increased amounts of 3-hydroxydodecanoic acid and 3-hydroxydodecenoic acid compared to the other two strains. PHA was detected in all three strains when nitrogen depleted below detectable levels in the growth medium. Strains GO16 and GO19 accumulate PHA at a maximal rate of approximately 8.4 mg PHA/l/h for 12 h before the rate of PHA accumulation decreased dramatically. Strain GO23 accumulates PHA at a lower maximal rate of 4.4 mg PHA/l/h but there was no slow down in the rate of PHA accumulation over time. Each of the PHA polymers is a thermoplastic with the onset of thermal degradation occurring around 308 degrees C with the complete degradation occurring by 370 degrees C. The molecular weight ranged from 74 to 123 kDa. X-ray diffraction indicated crystallinity of the order of 18-31%. Thermal analysis shows a low glass transition (-53 degrees C) with a broad melting endotherm between 0 and 45 degrees C.
本文描述了将石化聚合物聚对苯二甲酸乙二酯（PET）转化为可生物降解塑料聚羟基链烷酸酯（PHA）的过程。PET在450℃下进行热解，产生了固体、液体和气体馏分。液体和气体馏分被燃烧以回收能量，而固体馏分对苯二甲酸（TA）则用作细菌生产PHA的原料。先前报道能在TA上生长的菌株无法积累PHA。因此，我们从一家PET瓶加工厂中接触过PET颗粒的土壤中分离出细菌。从分离出的32株菌株中，选择了三株能够以TA作为唯一碳源和能源积累中链长度PHA（mclPHA）的菌株进行进一步研究。使用16S rDNA技术将这些分离株鉴定为恶臭假单胞菌（GO16）、恶臭假单胞菌（GO19）和弗雷德里克伯格假单胞菌（GO23）。恶臭假单胞菌GO16和GO19积累的PHA主要由3-羟基癸酸单体组成，而弗雷德里克伯格假单胞菌GO23积累的3-羟基癸酸是主要单体，与其他两株菌株相比，3-羟基十二烷酸和3-羟基十二碳烯酸的含量有所增加。当生长培养基中的氮含量降至可检测水平以下时，在所有三株菌株中都检测到了PHA。菌株GO16和GO19在12小时内以约8.4 mg PHA/l/h的最大速率积累PHA，之后PHA积累速率急剧下降。菌株GO23以4.4 mg PHA/l/h的较低最大速率积累PHA，但随着时间的推移，PHA积累速率没有放缓。每种PHA聚合物都是一种热塑性塑料，热降解起始温度约为308℃，在370℃时完全降解。分子量范围为74至123 kDa。X射线衍射表明结晶度约为18-31%。热分析显示玻璃化转变温度较低（-53℃），在0至45℃之间有一个较宽的熔融吸热峰。
