Well, the recirc does save fuel by reducing the bleed air required from the engines, but it's still bleed air (via the a/c packs) that does the pressurization. Even on a 747, one engine can keep the cabin pressure up.
But to keep it well distributed (prevent stagnant spots for passenger comfort) you either need multiple packs running (with a lot of excess cabin air escaping via the outflow valve), or fewer packs with the recirc fan(s) running.
All this will change with the 787 though.