Fungus grows in warmth and moisture which is a good description of a kitchen. Mold could shut your restaurant down. Best to consult a mold abatement company.

Fungus? Like mold? If so, perhaps try bleach, or taking out the wood and using something else. Fungus/mold in a restaurant is definitely not a good thing.

The wood has to reach what's called Equilibrium Moisture Content (EMC), which is different for various areas of the country/world. I don't know about end grain slabs, which is what you have, but the rule of thumb for lumber air drying (vs. kiln drying) is 1 year for each inch of thickness. Moisture leaves the end grain faster than the side and/or edge of the boards, so in your case the drying time will probably be shorter. If it is not dried in a controlled environment your slabs are going to split radially, due to drying too fast.

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