The invention relates to a process for the preparation of a fermentation product from lignocellulosic material, comprising the following steps: a) optionally, pretreatment of the lignocellulosic material, b) optionally, washing of the optionally pretreated lignocellulosic material, c) enzymatic hydrolysis of the optionally washed and/or optionally pretreated lignocellulosic material using an enzyme composition comprising at least two cellulases and whereby the enzyme composition at least comprises LPMO, and optionally purifying the hydrolysed lignocellulosic material, d) fermentation of the hydrolysed lignocellulosic material to produce a fermentation product, and e) optionally, recovery of a fermentation product, wherein the amounts of formed hydrolysed oxidation products at the end of the enzymatic hydrolysis by the oxidation by LPMO of the lignocellulosic material containing cellulose and/or cello-oligosaccharides is kept between 3 to 80 g/kg glucan present in the lignocellulosic material by adding a suitable amount of oxygen after the pre-treatment and before and/or during the enzymatic hydrolysis to the lignocellulosic material, preferably the formed hydrolysed oxidation product is gluconic acid, an aldonic acid and/or geminal diol, more preferably the hydrolysed oxidation product is gluconic acid.