It depends on what part of the fermentation we’re isolating. Ethanol is the pure alcohol that’s a product of fermentation, whereas a ferment lysate used in cosmetics is generally the entire system (lysate means that the cell walls have been ruptured).
It’d be like comparing yogurt (a mixture) to lactic acid (a pure substance).
The yeast used in brewing is filtered out of the final product and sold as a nutritional supplement, brewer’s yeast. Brewer’s yeast is rich with B vitamins, minerals, and proteins.
On the left is unfiltered beer, and on the right is filtered beer.
Hope that helps!