Dissecting the effect of chemical additives on the enzymatic hydrolysis of pretreated wheat straw

•Enzymatic hydrolysis of pretreated wheat straw in the presence of chemical additives.•Final substrate conversion enhanced by urea.•Late-stage hydrolysis rate enhanced by cetyl-trimethylammonium bromide.•Enzyme adsorption mainly affected by PEG8000.•Synergistic effect of combination of PEG8000 and urea.

Chemical additives were examined for ability to increase the enzymatic hydrolysis of thermo-acidically pretreated wheat straw by Trichoderma reesei cellulase at 50 °C. Semi-empirical descriptors derived from the hydrolysis time courses were applied to compare influence of these additives on lignocellulose bioconversion 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 (rlim) by 34% and reduced reaction time by 28%. A combination of PEG 8000 and urea increased sugar release more than additives used individually.