Abstract: Provided herein are compositions and methods related to the direct conversion of the starch in a ground or fractionated grain into a fermentable sugar feedstock capable of serving as a carbon source for the industrial production of one or more products by a fermenting organism, such as isoprene, isoprenoid precursor molecules, and/or isoprenoids. Such conversions may be performed at temperatures at or below the initial gelatinization temperature of the starch present in the grain and may utilize one or more isolatable endogenous enzymes present in certain unrefined grains.