The universe expanded from nothing, right? And black holes may be a "gate" to parallel universes, is it possible that stars that is being sucked in by black holes in our universe may be the origin of the energy in another universes "big bang"? Is there any theories that explains that?
Black holes are not really as exotic as popular media makes them out to be. Modern physics does not predict them to be "gateways" to other universes. Any matter that falls into a black hole gets crushed in the singularity at the center, and will remain there.
It's true that anything falling into a black hole becomes causally disconnected from the rest of the universe, but it's not correct to say that it enters a "different" universe.
The long-term future of all black holes is their eventual evaporation via Hawking radiation. In any case, the mass and energy before and after the black hole will remain in this universe.