以葡萄糖與戊酸鈉為碳源於限磷條件下連續發酵培養Ralstonia eutropha生合成PHBV之探討

Continuous Cultivation for Synthesis of PHBV by Ralstonia eutropha using Glucose and Sodium Valerate as Carbon Sources under a Phosphorus-Limited Condition

本研究探討Ralstonia eutropha於不同稀釋速率（0.155、0.115、0.0815、0.0604和0.0381 h^（-1））下，饋料培養基添加第二碳源戊酸鈉5.0 g／L對菌體生質量、聚羥基丁酯和戊酯的共聚物（poly-（hydroxybutyrate-co- hydroxyvalerate）, PHBV）生合成之影響。菌體生質量、PHBV生合成量、PHBV於總菌體中的含量及羥基戊酯（hydroxyvalerate, HV）於PHBV中的含量隨稀釋速率調降有先增加而後下降趨勢。稀釋速率為0.0815 h^（-1）時，具有最高之菌體生質量（5.94 g／L）、PHBV生合成量（1.54 g／L）、PHBV於總菌體中的含量（23.6％）及HV於PHBV中的含量（46.5％）。添加戊酸鈉之培養，生合成之PHBV中HV含量可達39.5-46.5％，較高HV含量可以改善PHBV脆性。葡萄糖之生質量產率係數0.713 g_（biomass）／g_（glucose）（稀釋速率為0.155 h^（-1））、葡萄糖之羥基丁酯（hydroxybutyrate, HB）產率係數0.056 g_（HB）／g_（glucose）（稀釋速率為0.1150 h^（-1））、戊酸鈉之HV產率係數0.123 g_（HV）／g_（valerate）（稀釋速率為0.0815 h^（-1））。添加戊酸鈉合成HV之效率較添加丙酸鈉為高。調整第二碳源添加之種類與添加量，可改變PHBV中HV含量，進而改變PHBV的性質。

In this study, Ralstonia eutropha was cultivated using sodium valerate (5.0 g/L) as a second carbon source to synthesize the biomass and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) under different dilution rates (0.155, 0.115, 0.0815, 0.0604, and 0.0381 h^(-1)). The biomass, PHBV biosynthesis, PHBV content in total cells, and HV content in PHBV increased and then decreased as the dilution rates decreased. When the dilution rate was 0.0815 h^(-1), the highest bacterial biomass (5.94 g/L), PHBV biosynthesis (1.54 g/L), PHBV content in total cells (23.6%) and HV content in PHBV (46.5%) were achieved. When sodium valerate was added, the HV content in PHBV reached 39.5%-46.5%. The high HV content can improve the brittleness of PHBV. The biomass yield coefficient (g_(biomass)/g_(glucose)) for glucose was 0.713 (diluting rate 0.155 h^(-1)), the HB yield coefficient (g_(HB)/g_(glucose)) for glucose was 0.056 (diluting rate 0.1150 h^(-1)), and the HV yield coefficient (g_(HV)/g_(valerate)) for valerate was 0.123 (dilution rate 0.0815 h^(-1)). The efficiency to synthesize HV using sodium valerate is higher than that using sodium propionate. Adjusting the type and amount of a second carbon source can change the HV content in the PHBV that may modify the properties of the PHBV.