Secretion of protein into growth medium

Torsten Boerchers borcher at
Sun Feb 18 12:03:53 EST 1996

Dear Natarajan,

Why did you expect at all that your recombinant protein
after secretion in the periplasm is further translocated
into the medium. To my knowledge this does normally not
happen, rather people are eagerly looking for hosts and
expression systems that allow secretion into the medium
e.g. staphyolococcus carnosus.

Could it be that with shaking flasks you somehow have
conditions that destroy the bacterial wall thus releasing
the recombinant protein in the medium? This might be due
to the high amounts of lysozyme that are formed with the
pETpLysS expression system.In a autocatalytical process 
some lysozyme set free e.g. by shearing of cells may cause
the lysis of other cells. This process may be reduced in the 

What do you think?

                          Torsten Boerchers                            /
    _/  _/_/_/ _/_/_/    Institute of Chemical- and Biochemical Sensor/
   _/  _/     _/   _/   Research (Molecular Biology Group)           /
  _/  _/     _/_/_/    Mendelstr 7, D-48149 Muenster, Germany       /
 _/  _/     _/    _/  Fax: +49-251-980 2890 Phone: +49-251-980 2880/
_/  _/_/_/ _/_/_/_/  E-Mail: borcher at              /

>   I am working with a bacterial gene which is secreted into the periplasmic
>space.  I cloned it under the control of T7 promoter and in expression studies
>in BL21DE3pLys grown in shake flasks, I found that the protein was secreted
>into the growth medium at very high levels(>100mg/liter).  I did the experiment
>in a fermentor and the results are very different.  It is not secreted into the
>medium!  My question is what is so different in a fermentor to cause this
>change in secretion.  I tried to reduce the dissolved air level in the
>in the fermentor.  This did not improve the situation.  What other parameters
>could be changed to get the protein secreted into the medium?  BTW the protein
>IS getting secreted into the periplasmic space.  Thanks in advance for your
>     Natarajan

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