Lewis was taken to the Port Macquarie Koala Hospital, which treated him for his injuries.
On Tuesday the hospital announced on Facebook that, sadly, Lewis' injuries were too severe for him to survive.
"Today we made the decision to put Ellenborough Lewis to sleep," it said.
"We placed him under general anaesthesia this morning to assess his burns injuries and change the bandages.
"We recently posted that 'burns injuries can get worse before they get better'.
"In Ellenborough Lewis's case, the burns did get worse, and unfortunately would not have gotten better."
According to the listing, as many as 350 koalas perished in and around Port Macquarie in November, so the goal is to build a “Koala Ark” to accommodate any surviving koalas.
It revealed the additional money will help to repopulate koalas in the wild, by establishing a breeding program to ensure the survival of the iconic marsupials.