The Microsoft AU Daemon is the small piece of software that periodically checks your Microsoft's servers to see if there are updates available for the Microsoft Office. Given that the Microsoft continues to release the security and other patches for the Office, it is probably the good idea to leave it running or at least you can remember to check manually if you already disable it.
For the time being, you can disable this app if you want by just opening any office program say Excel. In your help menu, Check for the Updates and just change "How would you like to check for updates" from the automatic to manual. Periodically (every month), it is always recommended that one should check it manually to install the any available update.