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"A fungus that can grow in maple syrup is not your average everyday mold, it’s a xerophile. Xerophiles grow in places that are too dry and hostile for your average fungus. OK, maple syrup is wet, but it’s also extremely high in sugar. All that sugar has the effect of pulling water out of cells, and the vast majority of fungi can’t grow in maple syrup at all."
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"...[M]aple syrup typically has a water activity of about 0.87 to 0.88, pretty hostile to most molds. Only a few xerophiles can live in it, including our surprise guest, Wallemia sebi."