以發酵槽培養探討放線菌利用甘油為碳源生產ε-聚離胺酸之研究

Investigation of ε-Poly-lysine Production by Streptomyces albulus in Fermenter Using Glycerol as Carbon Source

ε-聚離胺酸（ε-Poly-lysine；ε-PL）是由微生物發酵生產的天然生物性材料。ε-PL具有水溶、可食及生物可分解等特性且其本身或分解之產物對人體及環境不具毒性。由於具極佳的抑菌活性，水溶性強，熱穩定性高，食用安全，添加微量即能奏效，又不影響風味，因此在食品防腐領域得到廣泛應用。Streptomyces albulus DYU 1為本實驗室自行篩選並可利用甘油為碳源以生產ε-PL之菌株，本研究進行以發酵槽放大培養，並使用pH值控制及饋料策略以提高 S. albulusDYU 1生產ε-PL之產量，結果顯示採用二階段方式培養（即第一階段在pH值6.8之生長培養基培養36小時，待菌體生長完成再將其離心轉接至含有生產培養基之發酵槽內進行第二階段培養，並將pH值控制在4的條件下）可增加ε-PL的產量（由1.46 g/L增加至2.10 g/L）。另外在經一次饋料後，發現ε-PL之產量可提高至2.81 g/L（為未饋料之1.3倍），且為搖瓶培養之1.75倍。

ε-Poly-Lysine(ε-PL) is a naturally occurring biomaterial produced by microbial fermentation. It is water soluble, biodegradable, edible, nontoxic to humans, and environmentally safe. ε-PL shows a wide range of antimicrobial activity. Because it is stable at high temperatures and safe to eat, it is widely used as a food preservative; a trace amounts of ε-PL added to food can effectively preserve the food without altering its flavor. Our lab previously isolated Streptomyces albulus DYU 1, a bacterial strain capable of using glycerol as a carbon source for ε-PL production. In the present study, batch culture of S. albulus DYU 1 was conducted with a two-stage fermentation method in a 10-L jar fermentor; the bacteria were first cultivated in shake flask at pH 6.8 for 36 hours. The bacteria were then isolated and transferred into three media samples with pH levels controlled at 3.5, 4.0, and 4.5. After 10 days of incubation, glycerol consumption levels were 13.55, 17.38, and 19.47 g/L, and the ε-PL concentrations were 1.17, 2.10, and 1.78 g/L for media with pH levels of 3.5, 4.0, and 4.5, respectively. To optimize ε-PL production, back-feeding of glycerol was applied whenever the glycerol concentration was below 10 g/L. The final ε-PL concentration increased from 2.10 to 2.81 g/L (1.3-fold increase) after one feeding. This study provides a foundation for the future industrial production of this valuable biomaterial.