Hemoglobin–Laccase Modifications of Ligninsulfonate: A Promising Synergistic Stratagem for Lignin Biodegradation

Multicomponent systems, such as laccase cooperating with other proteins in ligninase, are able to modify the chemical structure of lignin efficiently and opens the door to potential applications. Here, an in-depth investigation of hemoglobin-assisted laccase oxidation of soluble lignosulfonate is carried out, using a combination of UV–visible spectroscopy, isothermal titration calorimetry, gel permeation chromatography, Raman spectroscopy, 2D nuclear magnetic resonance spectroscopy, and high-performance liquid chromatography–mass spectrometry. Intriguingly, hemoglobin enhances the exothermically oxidative process of the laccase reaction. Product characterizations suggest that hemoglobin may preferentially reduce the ratio of guaiacyl/syringyl subunits and promote phenylcoumaran formation simultaneously. The complicated interactions among hemoglobin, laccase, and lignin make a multiple-component reaction, suggesting that Fe-containing macromolecules have the capacity to mediate laccase based chemical modifications of lignin.