Maybe TSP (tri-sodium phosphate)? This and/or bleach will kill the mold, and might whiten the wood in the treated area slightly, but may also not completely remove the darker colored remains.
My Build: The Poet Creek Express
Poet Creek Or Bust
Engineering the TLAR way - "That Looks About Right"TnTTT ORIGINAL 200A LANTERN CLUB = "The 200A Gang"Green Lantern Corpsmen