Comparison of catalytically non-productive adsorption of fungal proteins to lignins and pseudo-lignin using isobaric mass tagging

Catalytically non-productive adsorption of fungal enzymes to pseudo-lignin (PL) was compared to adsorption to lignin preparations derived from different sources (SL, spruce; BL, birch; OL, beech) using different methods [steam pretreatment/enzymatic saccharification (SL, BL) and organosolv processing (OL)]. The protein adsorption to the SL was more extensive than the adsorption to the hardwood lignins, which was relatively similar to the adsorption to the PL. The adsorption patterns of 13 individual proteins were studied using isobaric mass tagging with TMTsixplex reagent and LC-MS/MS analysis. The results suggest that, on an average, adsorption of proteins equipped with carbohydrate-binding modules, such as the cellulases CBHI, EGII, and EGIV, was less dependent on the quality of the lignin/PL than adsorption of other proteins, such as β-Xyl, Xyn-1, and Xyn-2, which are involved in xylan degradation.