NOVELTY - Preparing (I) sugar product from ligno-cellulosic material, comprises: (a) optionally pre-treatment of ligno-cellulosic material; (b) optionally washing; (c) enzymatic hydrolysis of optionally washed and/or optionally pre-treated ligno-cellulosic material using enzyme composition comprising cellulases; and (d) optionally recovery of sugar product, where during part of time of enzymatic hydrolysis, oxygen is added and during part of the time of the enzymatic hydrolysis less oxygen is added.    USE - The process is useful for preparing a sugar and fermentation products from ligno-cellulosic material (claimed), producing ethanol, where the fermentation products include e.g. amino acids, vitamins, pharmaceuticals, animal feed supplements, plastics, solvents and fuels.    ADVANTAGE - The process: utilizes enzyme composition that retains activity for greater than or equal to 30 hours (claimed), hydrolysis reaction having reduced process time, optimized process conditions and enzyme at reduced dose; provides increased level of hydrolysis products; reuses the enzymes; is cost effective; allows increased glucose production; utilizes anaerobic and oxygen limited conditions; provides higher ethanol yields; utilizes a strain that use L-arabinose and optionally xylose during the production of ethanol; and lowers the risk of contamination during hydrolysis and contamination.    DETAILED DESCRIPTION - Preparing (I) a sugar product from ligno-cellulosic material comprises: (a) optionally pre-treatment of the ligno-cellulosic material; (b) optionally washing of the optionally pre-treated ligno-cellulosic material; (c) enzymatic hydrolysis of the optionally washed and/or optionally pre-treated ligno-cellulosic material using an enzyme composition comprising at least two cellulases; and (d) optionally recovery of a sugar product, where during part of the time of the enzymatic hydrolysis, oxygen is added to the ligno-cellulosic material and during part of the time of the enzymatic hydrolysis less oxygen is added to the ligno-cellulosic material compared to the other part of the time of the enzymatic hydrolysis, preferably no oxygen is added to the lignocellulosic material. An INDEPENDENT CLAIM is also included for preparing (II) fermentation product from ligno-cellulosic material comprising steps (a)-(c) as above per se, (d1) fermentation of the hydrolyzed ligno-cellulosic material to produce a fermentation product and (e) optionally recovery of a fermentation product