Researchers found that growing koji mold (Aspergillus luchuensis) alongside mouse immune cells in the laboratory significantly increases the production of valuable bioactive compounds. The mold releases enzymes called proteases that break down proteins from the animal cells, which the fungus then uses as building blocks to create medicinal compounds. This discovery shows that coculturing microorganisms with animal cells is an effective strategy to unlock hidden chemical production capabilities in fungi, which could lead to new medicines and useful compounds.