Answer:
PREPARATION OF TOXIN FIRST;suitable strain of microbes is taken and inoculated in sterile agar and is incubated till sufficient amount of toxin been produced.
then with a help of filtering materials such as ceramic filters are taken and bacteria along with its media containing toxin is allowed to filtered.then bacteria retain on filter while toxin along with media is collected as a filtrate.
thus this is again sterilized to remove any spores or unwanted metabolites present in media .this can be done due to solubility nature of exotoxin in water.this favours separation of toxin from bacteria.
PREPARATION OF TOXOID;then the sterilized toxin is mixed with the 25%HCHO and is incubated for 2-6 weeks.then all the toxicity of toxoid will be gone.but antigenicity property will remain as alike which is very important feature required for vaccines.
this toxoid prepared can be used as a such or further modified to still purer forms to prevent dangerous side effects caused in adults due to presence of unwanted metabolites of microbes.