Figure 4.

PCA analysis of the FTIR spectra in the 1800–700 cm⁻¹ wavenumber range. (A) Score plot of PC2 (32%) vs. PC1(47%); (B) loadings profile highlighting the bands that contributed most to the separation of lignin samples (n = 38 samples). (C) Results of one-way ANOVA on 10 bands identified in the loadings profile. Laccase activated lignins at pH 4.5, 5.0 and 6.0 with 0 and 13 U g⁻¹ lignin, with and without HBT, treated for 0, 0.5 and 2 h. Differences between pH levels of enzymatic treatment are significant at F statistic > 1 and p < 0.001 (in red) or p < 0.05 (in pink). The F test statistic is the ratio of two variances (variance between groups on variance within groups) and p value is the probability that determines if the difference between group means is statistically significant at 99.9% or 95%.