I have accidently put 49 litres of E85 in my 2006 Mazda3 Sport. What should I do? What damage will this do to the engine? The "check engine" light is on. PLEASE HELP!!!!!

 

Ethanol is corrosive to rubber. It can tolerate some ethanol but not this much. the engine itself will probably not take any damage since ethanol has a very high octane rating. However, expect misfiring.
What I would do: syphon most of the gas out of the tank and top off with regular fuel. You can later use the E-85 and mix it with regular, non ethanol fuel (no need to waste it).
If you can't syphon it out , keep adding regular fuel every time you get to about 1/2 full in order to dilute the ethanol.
After some time clear the codes by disconnecting the battery and stepping on the brake for a few seconds in order to erase the computer's memory.

I did a quick google search before giving this advise. This is my conclusion but I have not been in this situation myself. Let us know what you did and how it went.