How would you validate the cleaning process after producing Anthrax in a fermenter if you plan to follow it with a non spore forming product?

First of all we need to define validation for cleaning process.

that is nothing but ask yourself Are we performing right clenaing process?

Now we need to identify the objective of your validation.

Obective of the validation is already given in your question that is after cleaning process your fermentor must be free from spore forming gram positive bacillus.

Now we need to identify the purpose of clening process validation.

The pupose of the validation to ensure that what ever the cleaning procedure you follow to clean the fermentor, it has to be free from Bacillus spore formaing bacteria or any kind of contaminants. 

Thus after performing the cleaning process you need to verify the cleaning process is effective OR not.

Thus we need to defien what is verication.

Verification is nothing but ask yourself Are we performing the clenaing process in right procedure ?

Now how you going to get the answer for the  verifcation.

Usually for the cleaning process following analytical methods are done.

1. Direct surface smapling.

2 Rinse solution sampling.

There is one more verification method can be done to validate the cleanign process.

Placebo production: Where a small batch of product is processed and tested for any contaminants or residues.

Based on the scintific studies usually spore forming bacteria area more resistant to temeprature and chemaicals, thus you need to identify the right cleaning procedure to eradicate or elimiante the all spores and spore forming bacteria from the fermentor.As per my knowledge and reading farmaldehyde is effective to control spore forming bacteria.

In your case you may need to follow multiple step of cleaning process.

This really hard Question , for my self , I did not work in biotechnology field but if you need brainstorming ,

We need to agree at first that m.o not like chemicals , no equal distribution , you need to search every where and you need to sample the whole system to confirm removal of all m.o

I think a media fill run(s) after the spore forming m.o. will assure that all remaining of the m.o has been removed effectively

by this way you will  assure sterilization of the line and removal of all living m.o

another approach is applying SIP with heat treatment assuring FO above or may reach to , double SIP for extra assurance

The use of dedicated pipe lines and change parts will be helpful and give extra assurance

Kindly review , and feedback , if my answers seems inapplicable , kindly tell me as I enjoy disscusing issues and gain knowledge