Catalyzes the formation of feruloyldiketide-CoA by condensing feruloyl-CoA and malonyl-CoA in the curcuminoid biosynthesis. Has no activity with cinnamoyl-CoA. (E)-feruloyl-CoA + H(+) + malonyl-CoA = (E)-feruloylacetyl-CoA + CO2 + CoA 4-coumaroyl-CoA + H(+) + malonyl-CoA = (4-coumaroyl)acetyl-CoA + CO2 + CoA kcat is 0.67 min(-1) with malonyl-CoA. Optimum pH is 6.5-7.5. Optimum temperature is 25-35 degrees Celsius. Secondary metabolite biosynthesis; flavonoid biosynthesis. Homodimer. Expressed in both the leaf and rhizome, with higher expression in the rhizome. Belongs to the thiolase-like superfamily. Chalcone/stilbene synthases family.