For those with no LE Bluetooth:
It works with my old MacBook Pro (13-inch, Mid 2009 - OSX El Captain). I'm using the Asus BT400 USB adapter. After you insert the adapter, you have to open the Terminal app (in Utilities folder) and type this code:
sudo nvram bluetoothHostControllerSwitchBehavior=alwaysPress enter and the app will ask for your password. After typing your password and hitting enter again, all you have to do is reboot your Mac.
You just have to do it once. After that, insert the adapter whenever you want to use Bluetooth Low Energy and it's done!