In my childhood, we had these kinds of root vegetables sliced and caved in on one end, and a spoonful of honey was placed on top and in the cavity. Somehow this sped up conversion to overnight, and it was a treat. I guess, similar process could be used to convert them for brewing.

Although the whole idea sounds a bit like potato for vodka. Nothing wrong with that too, but the flavor might me less than interesting in the end. Worth trying I guess. I wish I had some of those now, not unripe ones from the store.