| Summary: | 碩士 === 元智大學 === 生物科技與工程研究所 === 98 === Polyhydroxyalkanoates (PHAs) have received much attention because of their similarity to conventional plastics and their complete biodegradability. Both of Cupriavidus taiwanensis and Pseudomonas putida are able to accumulate PHAs when the carbon substrate is in excess to other nutrients such as nitrogen, sulfur, phosphorus or oxygen. The PHAs produced by C. taiwanensis and P. putida are scl-PHAs (mainly PHB) and mcl-PHAs, respectively. In addition, many species/strains of Cupriavidus and Pseudomonas were also known to possess heavy metal resistant traits. Therefore, we aim to characterize the PHAs/PHB accumulation in the presence or abesence of heavy metals cadmium in these microorganisms, including the type of PHAs produced as well as the amount accumulated.
When P. putida KT2442 and C. taiwanensis EJ02、184、187 were cultivated in the medium(LB broth) containing cadmium, the results showed that the cadmium (Cd) tolerance of P. putida KT2442 and C. taiwanensis EJ02, 184, 187 were 0.75 mM, 6 mM, 1 mM, 1 mM respectively. When the same medium supplemented with 15 g/L sodium gluconate, C. taiwanensis 187 will increase its tolerance to cadmium to 1.5 mM. There is no significant difference of PHB content (analyzed by gas chromatography) in strain EJ02 grown in the Luria Bertani (LB) medium with and without cadmium. PHB accumulation was slightly enhanced by supplemented with sodium gluconate as an extra carbon source in LB medium. However, this phenomenon was not observed in C. taiwanensis 184. The possible relationship of PHB accumulation and the presence of heavy metal (for example cadmium) in the medium in these C. taiwanensis is remained to be studied.
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