Potato infusion lab grade additive for fungal agar media

This is lab grade potato infusion, no more potato flakes / starch / mash potato. 

Heres an easy recipe so you make Potato Dextrose Agar (with extras)

PDA base recipe

1ltr distilled water
20g agar
20g dextrose
4g Potato infusion

optional

2g yeast (for PDYA)
2g activated charcoal (for charcoal PDYA)