NOVELTY - Increasing recovery of glucose from a pre-treated ligno-cellulosic biomass comprises: (A) exposing a composition to a vacuum condition; (B) ceasing to expose the composition to the vacuum condition; (C) adding at least one catalyst to the composition where the catalyst is capable of hydrolyzing the water insoluble pre-treated ligno-cellulosic biomass in the composition; and (D) Conducting a catalytic hydrolysis of the water insoluble pre-treated ligno-cellulosic biomass in the composition.    USE - The method is useful for increasing recovery of glucose from pre-treated ligno-cellulosic biomass (claimed).    ADVANTAGE - Improved pre-hydrolysis step involving exposing water insoluble pre-treated ligno-cellulosic biomass to vacuum conditions, with and without enzymes is provided. The result is an increased yield of glucose and often xylose after the enzymatic hydrolysis when compared to a composition which has not been exposed to vacuum conditions.    DETAILED DESCRIPTION - Increasing recovery of glucose from a pre-treated ligno-cellulosic biomass comprises: (A) exposing a composition to a vacuum condition, where the composition has a dry matter content, and the composition comprises a water insoluble pre-treated ligno-cellulosic biomass produced from a ligno-cellulosic biomass processed in a pre-treatment process, and an added liquid which has been added to the water insoluble pre-treated ligno-cellulosic biomass after the pre-treatment process, where the wt.% of the dry matter content of the composition by weight of the total amount of the composition is in the range of 1 to 60 wt.%; (B) ceasing to expose the composition to the vacuum condition; (C) adding at least one catalyst to the composition where the catalyst is capable of hydrolyzing the water insoluble pre-treated ligno-cellulosic biomass in the composition; and (D) Conducting a catalytic hydrolysis of the water insoluble pre-treated ligno-cellulosic biomass in the composition; or increasing recovery of glucose from a pre-treated ligno-cellulosic biomass, comprises: (A) exposing a composition to a vacuum condition, where the composition has a dry matter content, and the composition comprises water insoluble pre-treated ligno-cellulosic biomass, where the wt.% of the dry matter content of the composition by weight of the total amount of the composition is in the range of 1 to 60 wt.%, and the composition is void of free liquid; (B) ceasing to expose the composition to the vacuum condition; (C) adding at least one catalyst to the composition where the catalyst is capable of hydrolyzing the water insoluble pre-treated ligno-cellulosic biomass in the composition; and (D) conducting a catalytic hydrolysis of the water insoluble pre-treated ligno-cellulosic biomass in the composition; or increasing recovery of glucose from a pre-treated ligno-cellulosic biomass, comprises: (A) exposing a composition to a vacuum condition, where the composition has a dry matter content, and the composition comprises water insoluble pre-treated ligno-cellulosic biomass, and a free liquid, where the wt.% of the dry matter content of the composition by weight of the total amount of the composition is in the range of 1 to 60 wt.%; (B) ceasing to expose the composition to the vacuum condition; (C) adding at least one catalyst to the composition where the catalyst is capable of hydrolyzing the water insoluble pre-treated ligno-cellulosic biomass in the composition; and (D) conducting a catalytic hydrolysis of the water insoluble pre-treated ligno-cellulosic biomass in the composition. An INDEPENDENT CLAIM is a product produced by a process to increase the recovery of glucose from a pre-treated ligno-cellulosic biomass, the process comprises: (A) exposing a composition to a vacuum condition, where the composition has a dry matter content, and the composition comprises at least one gas and a water insoluble pre-treated ligno-cellulosic biomass comprised of an amount of water insoluble carbohydrates produced from a ligno-cellulosic biomass processed in a pre- treatment process, and an added liquid which has been added to the water insoluble pre-treated ligno-cellulosic biomass after the pre-treatment process, where the wt.% of the dry matter content of the composition by weight of the total amount of the composition is in the range of 1 to 60 wt.%; and (B) ceasing to expose the composition to the vacuum condition so that the amount of the gas in the product is less than the amount of the gas present prior to the vacuum exposure and the amount of water insoluble carbohydrates prior to the vacuum exposure is the same as the amount of water insoluble carbohydrates after exposure to the vacuum.