The basidiomycete brown rot fungus Neolentinus lepideus is capable of assimilating and fermenting lactose to ethanol with a conversion yield comparable to those of lactose-fermenting yeasts. The ability of the fungus to ferment lactose is not influenced by the addition of glucose or calcium. Therefore, N. lepideus may be useful in ethanol production from materials composed mainly of lactose, such as cheese whey or expired cow’s milk. Whey is a by-product of cheese manufacturing, and approximately 50% of the total worldwide production of whey is normally disposed of without being utilized. We found that N. lepideus produced ethanol directly from cheese whey with a yield of 0.35 g of ethanol per gram of lactose consumed, and it also fermented expired milk containing lactose, protein, and fat with a similar yield. Our findings revealed that the naturally occurring basidiomycete fungus possesses a unique ability to produce ethanol from cheese whey and expired milk. Thus, N. lepideus may be useful in facilitating ethanol production from dairy wastes in a cost-effective and environmentally friendly manner.

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