There is mold killer stuff that's sold at paint stores. If you don't
want to use bleach, try that. It doesn't take much bleach, try a very
dilute solution. Lysol will do it as well. You need to figure out
where the moisture is coming from that allows the mold to grow.
Probably lack of ventilation, or condensation if you're in a cold
climate. Vinegar should also do the trick, while not the best smelling
solution.