I had the same problem with my ASUS K53E.

sudo apt-get install git



git clone git://git.iksaif.net/acpi4asus-dkms.git



cd acpi4asus-dkms 



make 



sudo make install



sudo modprobe asus-nb-wmi  

After every kernel update the above will be erased and you will need to re-do it every time until it is included in a kernel version at a later stage. To make it easier create a .deb package which will be easier to install.

sudo apt-get install debhelper 



cd acpi4asus-dkms 



dpkg-buildpackage



sudo dpkg -i [newly-created-package].deb



sudo modprobe asus-nb-wmi

source

I have a little different computer though; mine is a K53E and yours is an X53S, so I can't guarantee that it'll work.