I don't work with Fusaria, but I would filter the broth to get the mycelium and then use whether method suits you - grinding with pestle and mortar in buffer, ball mill. enzymatic disruption of the cell wall...

Hi: you can use freeze dryer technique to dry the mycelium and grind it with pestle.  

or you can use DNA extract kit that no required liquid nitrogen .

Grinding method after culturing the fungus on broth medium then add protease enzyme to destroy the cell membrane and nuclear membrane