Some products such as solvents, e.g., butanol, are toxic to solvent-producing microorganisms, yet fructose metabolism can facilitate the increase of protective substrates such as triglycerides, which can protect the microorganism from the toxic effect of the product. Methods are provided for producing a product, e.g., a solvent from fructose derived from a cellulosic or lignocellulosic material. Using the methods herein, a fructose solution can be fermented to a solvent more rapidly, and with better yields, than a glucose solution.