BACKGROUND: Solvent based pretreatment of biomass followed by enzymatic hydrolysis (in the presence of the solvent- 'in situ hydrolysis') is an attractive route to develop a biorefinery concept since it reduces a number of washing steps to remove the solvent and saves energy. This work explores the ability of the commercial 'Iyocell' solvent- N-methyl Morpholine N-Oxide (NMMO) for 'in situ' hydrolysis at high cellulose loadings and compares its hydrolysis performance with commercially available ionic liquids (ILs). RESULTS: NMMO is able to dissolve high loadings of cellulose which on subsequent in situ enzymatic hydrolysis results in not only an increased sugar yield (similar to 30 mg mL(-1)) but also an enhanced rate of hydrolysis (12.24 mg mL(-1) h(-1)). In addition, a comparative study of hydrolysis in the presence of NMMO and ILs reveals the fact that hydrolysis in NMMO produces the highest sugar yields when compared with ILs. CONCLUSION: This study thus establishes the effectiveness of NMMO as a pretreatment solvent- it is an excellent solvent for disrupting the microstructure and dissolving high loadings of cellulose, and hydrolysis reactions can be carried out in the presence of NMMO since enzymes are active in its presence. (C) 2016 Society of Chemical Industry