How to avoid formation of fungi in our product?

We are creating a new product which is basically wood shavings with colorant. The colorant is applied with water in a very economical way. The final product is a bit moist and we are worried that it might generate fungi after we seal pack it in plastic bags. So we either need some kind of preservative and the know how to apply it, that will avoid formation of fungi. The other alternative would be to find an economical way to dry the product.How to avoid formation of fungi in our product?
before packing use ultraviolet disinfector!








Also you can use the solution of potassium permangnate (KMnO4) it works better but check for its application. It may not harm your product.