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.