Chemical additives were examined for ability to increase the enzymatic hydrolysis of thermo-acidically pretreated wheat straw by Trichoderma reesei cellulase at 50 degrees C. Semi-empirical descriptors derived from the hydrolysis time courses were applied to compare influence of these additives on lignocellulose bio-conversion on a kinetic level, presenting a novel view on their mechanism of action. Focus was on rate retardation during hydrolysis, substrate conversion and enzyme adsorption. PEG 8000 enabled a reduction of enzyme loading by 50% while retaining the same conversion of 67% after 24 h. For the first time, a beneficial effect of urea is reported, increasing the final substrate conversion after 48 h by 16%. The cationic surfactant cetyl-trimethylammonium bromide (CTAB) enhanced the hydrolysis rate at extended reaction time (r(lim)) by 34% and reduced reaction time by 28%. A combination of PEG 8000 and urea increased sugar release more than additives used individually. (C) 2014 Elsevier Ltd. All rights reserved.