Hi!

can you be more specific about your question.Are you talking about the expression of recombinant protein? which cells you are using to express your protein? if you can answer me then i can tell you the method in detail..

Hi

Gaurav is correct, can you please give us more detail.

From what I can make out of the question.If I am expressing using E.coli under a lac or Arabinose operon. I normally use 0.4 - 0,5 % Glucose. I add the glucose to the overnight enrichment culture and also add it when I subculture from the O/N into the expression medium. When cells reach the correct OD...you then add IPTG/Arabinose

Kind regards

I'm sorry for my little explanation. i want to optimize expression of recombinant pro in pET21a(+). I use BL21(DE3) to express my protein.

Hi Fereshteh!!

if you are taking about the enhancing your protein expression, in that case you have to optimize the glucose percentage starting from 2% to 10% (sometimes till 20%) W/ V.You add glucose at the initial time when you inoculate your culture. i used to add glucose directly to the media at the time of inoculation,( you can add glucose powder directly to media or you can prepare a filtered glucose stock solution). Apart from glucose you can use sorbitol or ethanol, it works better then glucose..after you gets the OD of 0.5 then induced with 0.5mM of IPTG..

Try this method if any doubt or further query can write me here..

Good luck.

hi Gaurav

tnx for your giud. I try it. but how much sorbitol or ethanol is useful?

Sorbitol you can optimize with 2%- 20% and ethanol is 1% - 3%..

Hi

Thank for the additional information. Gaurav, does the ethanol play a role in silencing the promoter or does it have other effect. (I have never used, seems interesting)

In addition to what we have have mentioned, make sure you do not autoclave the glucose as it will caramelise and can lead to you getting your protein in inclusion bodies...rather make a stock solution as also suggested by Gaurav

Kind regards