NOVELTY - Producing a fermentation product in a fermentation system from biomass that has been pre-treated and separated into a first component and a second component comprises: supplying the first component to the fermentation system; providing an ethanologen to the fermentation system; maintaining the first component and ethanologen in the fermentation system at 26-37 degrees C and a pH of 4.5-6 for a time of no less than 18 hours; and recovering the fermentation product from the fermentation system.    USE - The method is useful for producing a fermentation product, preferably ethanol (claimed).    DETAILED DESCRIPTION - Producing a fermentation product in a fermentation system from biomass that has been pre-treated and separated into a first component and a second component comprises: supplying the first component to the fermentation system; providing an ethanologen to the fermentation system; maintaining the first component and ethanologen in the fermentation system at 26-37 degrees C and a pH of 4.5-6 for a time of no less than 18 hours; and recovering the fermentation product from the fermentation system, where the ethanologen is supplied to the fermentation system at a concentration of less than 150 g of ethanologen on a dry basis per liter of first component, the biomass comprises lignocellulosic material, the lignocellulosic material comprises at least one of corncobs, corn plant husks, corn plant leaves and corn plant stalks, the first component comprises pentose, the pentose comprises xylose, and the ethanologen is capable of fermenting xylose into ethanol. INDEPENDENT CLAIMS are included for:    (1) a fermentation system configured to produce a fermentation product from biomass that has been pre-treated and separated into a first component and a second component, comprising a first vessel configured to receive the first component and an ethanologen, and a second vessel configured to propagate the ethanologen for supply to the first vessel, where the first vessel is configured to maintain the first component and ethanologen at 31-34 degrees C and at a pH of 5.2-5.8 for a time of no less than 18 hours; and    (2) a biorefinery for producing a fermentation product from biomass comprising a preparation system to prepare the biomass into prepared biomass, a pre-treatment system to pre-treat the prepared biomass with a dilute acid for separation into a first component from which pentose can be accessed for fermentation and a second component from which hexose can be made available for fermentation, a first treatment system to treat the first component into a treated first component by removing removed components from the first component, a first fermentation system to produce a first fermentation product from the pentose by supplying an ethanologen and maintaining the first component and ethanologen at 26-37 degrees C and at a pH of 4.5-6 for a time of no less than 18 hours, a distillation system to recover ethanol from the first fermentation product, a treatment system to process removed components.    DESCRIPTION OF DRAWING(S) - The figure shows a perspective view of a biorefinery comprising a cellulosic ethanol production facility.