You don't mention which OS you are on. If you are on a *nix box you can use split.

Split the file into equal parts and just run multiple instances of your application.

At least that's one way. However, have you considered that the extraction process isn't actually what needs optimizing? If you are running through a list of regex on each line, I'd hazard a guess that that is consuming more of your time than reading each line in. It might help if you'd post some of your code so we can take a gander and see where your bottleneck is.