He added: "He was very hard to fight but you can't anything about it. Now I'll spend some time with my family and see what happens next."
Soliman improved to 42-11 and is now set to fight Daniel Geale, who defeated Sturm last year, for the IBF crown.
There was a moment of confusion at the end of the bout as Michael Buffer announced the judges had awarded it to Sturm before correcting himself as the German and the crowd were celebrating.