NOVELTY - 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, comprises 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. 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 not less than 18 hours, the biomass comprises lignocellulosic material, and the first component comprises pentose which is xylose.    USE - The fermentation system is useful for producing a fermentation product from biomass, where the fermentation product is ethanol (all claimed).    ADVANTAGE - The fermentation system facilitates improvement in the efficiency and yield of cellulosic ethanol from biomass.    DETAILED DESCRIPTION - 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, comprises 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. 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 not less than 18 hours, the biomass comprises lignocellulosic material, where the lignocellulosic material comprises at least one of maize cobs, maize plant husks, maize plant leaves and maize plant stalks, and the first component comprises pentose which is xylose. An INDEPENDENT CLAIM is also included for 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 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 not less than 18 hours; a distillation system to recover ethanol from the first fermentation product; and a treatment system to process removed components.