Bi-carbonate of soda is the thing to use in fridges. For grease and such, lemon juice.

It sounds like you may have some spores in a crack somewhere. If so, the fridge will have to go. The thing about molds is that once infected they are very hard to get rid of. You could try an anti-mold spray, however experience tells me the you will have to buy a new one.

Sorry to be such a harbinger.