# Bivolarization of Grape Stalks as Animal Feed by Solid State Fermentation Using White-Rot Fungi
## 3 Results and Discussion
edodes_, which maintained the peak until 42 days of incubation (2.77 U g\({}^{-1}\) DM; \(p\) < 0.001). Higher LnP activities were also measured for longer incubation periods, with _L. edodes_ presenting the highest production at 42 days of incubation (2.33 U g\({}^{-1}\) DM; \(p\) < 0.001). It should be noticed that no LnP activity was detected for _P. eryngii_ in any of the IPs. Studies have shown that for several white-rot fungi strains, activities of MnP and lactose are predominant [33] and that LnP activities are not always detected [53]. Nevertheless, one must refer that the efficient segregation of lignocellulosiculolytic enzymes during the SSF fungal treatment of agro-industrial wastes is quite variable and it depends on several factors such as the strain specificity, duration of incubation periods and incubation conditions. The effects of the interaction between the IP and the fungi clearly denote these differences, enhancing the differential behavior of the different fungi according to the IP. The cellulolytic enzymes avicelase, and CMCase presented the same kinetics for all fungi strains, showing a peak at 14 days of IP for _L. edodes_ and _P. eryngii_ and 28 days for _P. citrinopileatus_. The highest activities were once again detected for _L. edodes_ (0.58 and 1.51 U g\({}^{-1}\) DM, for avicelase and CMCase, respectively). For the enzymes involved in hemicellulolysis, xylanase and FAEs, production peaks were attained at 42 days of IP for both _L. edodes_ and _P. citrinopileatus_ while for _P. eryngii_ the same trend was observed for FAEs but not for xylanase, with a peak at 14 days. Again, _L. edodes_ showed a higher production of these enzymes (2.96 and 1.38 U g\({}^{-1}\) DM for xylanase and FAEs, respectively). These results are consistent with the data presented in Table 1. In fact, the treatment with _L. edodes_ had the higher degradability of lignin (at 42 days of IP), consistent with the higher activity values for all enzymes, although there were differences within the period in which the activity peak was achieved. As it has been previously reported [33], lignin degradation is the result of a synergistic engagement of several enzymes that promote ligninolysis efficiency, depending on the fungal strain. In order to better explain this variability, the experimental data were submitted to a PCA analysis (Figure 3). Eigenvalues from the PCA indicated that the first two principal components (PC) accounted for 83.6% of the total data variance (PC1: 62.7% and PC2: 20.9%). Axe PC1 was positively correlated to NDF, ADFom, and lignin content, and negatively with the IVOMD, C/L ratio, enzymes involved in ligninolysis (Lacc, MnP, and LnP), and hemicellulolysis (Xylanase and FAEs). Axe PC2 was positively correlated with cellulose, and negatively with hemicellulose, CP content and enzymes involved in cellulolysis (avicelase and CMCase). PCA showed that treatment with _P. eryngii_ is correlated with a high content of cellulose, NDF, ADFom, and lignin, _P. citrinopileatus_ is correlated with a higher production of cellulolytic enzymes but inversely correlated with the HC content (longer IP, lower HC content), and _L. edodes_ is correlated with a high ratio of C/L, a higher IVOMD, and a higher  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**IP** & **Fungi** & **Lacc** & **MnP** & **LnP** & **Avicelase** & **CMCase** & **Xylanase** & **FAEs** \\ \hline
7 & _L. edodes_ & 0.114  & 0.339  & 0  & 0.200  & 0.409  & 0.477  & 0.144  \\  & _P. citrinopileatus_ & 0.279  & 0.087  & 0.159  & 0.879 [FOOTNOTE:7]Footnote 7: Values with different letters within a column are significantly (\(p<0.05\)) different. & 0.120 [FOOTNOTE:7]Footnote 7: Values with different letters within a column are significantly (\(p<0.05\)) different. & 0.092 [FOOTNOTE:7]Footnote 7: Values with different letters within a column are significantly (\(p<0.05\)) different. & 0.179 [FOOTNOTE:7]Footnote 7: Values with different letters within a column are significantly (\(p<0.05\)) different.