The impact of active site protonation on substrate ring conformation in Melanocarpus albomyces cellobiohydrolase Cel7B

Understanding how the protonation state of active site residues impacts the enzyme's structure and substrate conformation is important for improving the efficiency and economic viability of the degradation of cellulosic materials as feedstock for liquid fuel and value-added chemicals.

Characterization of fractionated lignins polymerized by fungal laccases

Lignins are important biopolymers that can be converted into value-added materials by enzymatic treatments. However, the heterogeneity of the lignin polymer makes it a challenging material to modify. Thus, chemical fractionation was used to obtain lignins with high homogeneity in order to assess their biotechnological utilization. Commercial Alcell, birch organosolv lignins, and steam-exploded pine and eucalypt lignins were sequentially fractionated by ether, ether/acetone 4:1 (v:v), and acetone. All fractions were structurally characterized prior to treatments with Thielavia arenaria, Trametes hirsuta, and Melanocarpus albomyces laccases. The reactivities of the enzymes towards the lignins were determined by oxygen consumption measurements, and the degree of polymerization was confirmed by size exclusion chromatography. Field emission scanning electron microscopy revealed that the surfaces of the lignin nanoparticles were dispersed in the enzyme treatment, suggesting an increase in hydrophilicity of the surfaces detected as loosened morphology. Hence, it was concluded that enzyme-aided valorization is an attractive means for lignin modification, provided that optimum reaction conditions are employed.

Activation of thermomechanical pulp by laccases as studied by UV-Vis, UV resonance Raman and FTIR spectroscopy 10th EWLP, Stockholm, Sweden, August 25–28, 2008

The changes in lignin structure of spruce thermomechanical pulp (TMP), induced by treatment with laccase of Trametes hirsuta (ThL) and laccase of Melanocarpus albomyces (MaL), has been investigated by UV-Vis, UV resonance Raman (UVRR), and Fourier transform infrared (FTIR) spectroscopy. The spectroscopic results showed that the structural changes were small; however, the changes were slightly more pronounced in the case of MaL. Nevertheless, the brightness of the pulps remained higher after treatment with MaL than after treatment with ThL. Accordingly, MaL is a promising enzyme for fiber activation and functionalization.