Figure 5

HSQC NMR spectra of raw and pretreated cellulolytic enzyme lignin in the aromatic region: (a) raw; (b) 20 mL/min, 140°C, 12 min; (c) 20 mL/min, 140°C, 192 min; (d) 20 mL/min, 180°C, 12 min; (e) 20 mL/min, 180°C, 192 min; (f) 0 mL/min, 140°C, 192 min; (g) 0 mL/min, 180°C, 12 min. Identified units include p-hydroxyphenyl (PB_{2, 6}), guaiacyl (G₂, G_5, G₆), syringyl (S_{2, 6}), and oxidized syringyl (S’_{2, 6}) units. Signal assignments are presented in Table 4.