自動(dòng)誘導超級肉湯培養基Super Broth產(chǎn)品描述：

自動(dòng)誘導超級肉湯培養基(Autoinductive Super Broth)也稱(chēng)自動(dòng)誘導SB，用于大腸桿菌Lac啟動(dòng)子驅動(dòng)的的重組蛋白表達，無(wú)需添加IPTG。自誘導培養基能夠獲得高細胞密度，蛋白表達率高出IPTG誘導過(guò)程好幾倍。

SB自動(dòng)誘導培養基工作原理

SB培養基由于其高密度的營(yíng)養成分，非常適合重組大腸桿菌的快速生長(cháng)。超級肉湯培養基是一種加富培養基，配方基于TB培養基（Terrific Broth），后者由LB培養基改進(jìn)而來(lái)，目的是達到高細胞密度。E. coli在該培養基中生長(cháng)速度快于其在LB培養基或 2x YT肉湯中的生長(cháng)速度。SB培養基被認為是很佳的質(zhì)粒擴增培養基。一般來(lái)說(shuō)，在液體培養基中大腸桿菌細胞生長(cháng)的質(zhì)量如下：LB Broth < 2x YT Broth < Terrific Broth < Super Broth。

該培養基中含有理想比例的葡萄糖和α-乳糖作為碳源和能量來(lái)源。胰蛋白胨提供氮源、維生素、礦物質(zhì)和氨基酸，這些營(yíng)養成分是細胞生長(cháng)所必需的。酵母提取物是豐富的B族維生素來(lái)源。Studier salts為細菌細胞的生長(cháng)提供很佳的生理環(huán)境。

通常，外源蛋白在細菌中表達時(shí)常使用IPTG誘導的啟動(dòng)子，如Lac啟動(dòng)子。當細胞密度達到理想值時(shí)，通過(guò)向培養基中加入IPTG的方法誘導蛋白表達。使用這個(gè)自動(dòng)誘導培養基，不再需要監測細胞密度和添加IPTG。葡萄糖作為半乳糖操縱子的阻遏因子阻止細菌利用α-乳糖，而被優(yōu)先代謝，促進(jìn)高密度生長(cháng)。一旦培養基中的葡萄糖被耗盡（通常發(fā)生在對數期的后期），乳糖被?-半乳糖苷酶轉換成異乳糖（葡萄糖-1,6-半乳糖），而后者作為IPTG誘導型啟動(dòng)子的誘導劑，引起乳糖阻遏子從與DNA結合的位點(diǎn)上釋放，啟動(dòng)重組蛋白的表達。對于DE3基因型的E.coli中，異乳糖使T7lac啟動(dòng)子去阻遏，并誘導lacUV5啟動(dòng)子表達T7 RNA聚合酶。通過(guò)這種方式，在細菌培養物生長(cháng)到某一特定點(diǎn)時(shí)蛋白表達自發(fā)開(kāi)始，去掉了監測細胞密度（OD600）和添加IPTG這兩個(gè)步驟。與傳統IPTG誘導的蛋白表達過(guò)程相比，使用自動(dòng)誘導培養基極大地方便和簡(jiǎn)化了試驗流程。

使用步驟：

1. 稱(chēng)取74.85 脫水培養基粉末，用1L去離子水加熱溶解。

2. 煮沸1min。

3. 115°C 滅菌20min。

不要過(guò)度加熱，避免乳糖分解和培養基顏色加深。冷卻后保存在2-8oC，如果不染菌，可以保存2個(gè)月左右。

Quantity: 500g

Appearance: Beige powder. Autoclaved medium should be amber.

Storage: 2oC – 25oC. When not in use, keep container closed to avoid hydration.

配方Formulation (g/L)

Tryptone: 35.00

Yeast Extract: 20.00

MgSO4: 0,15

(NH4) 2SO4: 3,30

KH2PO4: 6,80

Na2HPO4: 7,10

Glucose 0,50

Alpha Lactose 2,00

Final pH (25oC): 7,0 ± 0,2

配置Preparation:

Add 45,85g of the dehydrated medium to one liter of distilled water. Mix well and dissolve by heating with regular agitation. Boil for 1 minute in order to dissolve completely. Dispense in appropriate containers and sterilize by autoclaving at 121oC for 15 to 20 minutes. Store at 2oC to 8oC.

使用Usage

Commonly, heterologous protein expression is carried out in bacterial systems where the expression is under the control of an IPTG-inducible promoter, such as the Lac promoter. Cells are grown until a desired density and protein expression is subsequently induced by adding IPTG to the medium. With this Auto Induction Medium (AIM), it is no longer required to monitor cell density and to add IPTG at the proper stage, as the medium contains an optimized ratio of glucose and alpha lactose as carbon sources. Glucose, who serves as a repressor of the Lac operon, by preventing uptake of alpha lactose (hence and IPTG) is metabolized preferentially during growth, promoting high cell density. Once glucose is depleted, usually in mid to late log phase, lactose enters the cell where it is converted by ?galactosidase into allolactose, which in turn serves as the inducer of the IPTG-inducible promoter, resulting in protein expression. This is a great convenience and simplifies manual or automatic induction and analysis of multiple clones compared to conventional IPTG  induction.