i found a board for boosting dc to dc, but i am not sure if it is possible. This is for a "can I do it project, for my jr high kids to see. i want to make a potato battery and see how many potatoes i will need to get 12v using a booster.
i found this to buy online.
Arduino] DCDC (LC) LM2577 Step-Up Module INPUT 3.5-35 V OUTPUT 5-56 V
would it do the job?
The booster circuit needs current itself, I'm not sure a potato can make a normal booster circuit work.
In theory it should be possible, and there are many low current and efficient chips, for example LTC3105.
Perhaps a power energy harvester chip can be used, for example LTC3330.
It might be possible to make a circuit yourself without a special chip. But then I would try a voltage multiplier with Schottky or Germanium diodes.
salty pateto ,, gives more current 
you need a lot of pateto's , better use oranges ,, you wl need less ,,
you probely want them to make free energy ,
you wil like this