# Effective Use of Flax Biomass in Biorefining Processes
## 3 Results and Discussion
### Biocomposite Production Process
#### 3.3.3 Microbiological Properties of Biocomposites  
In the mold fungal test, regardless of the type of linen biomass, the growth of test fungi was observed on the surface of the tested samples inoculated with microorganisms (series I). The results of the test are shown in Figure 4.  
The highest mold fungi resistance was found for biocomposites PLA-LS-20--fungal growth was insignificant (second degree), in the form of single traces of fungi on the surface of the samples. Biocomposites PLA-FF-20 were the most susceptible to the test fungi. Intensive fungal growth (fourth degree) was observed on the samples, covering more than 50% of the tested surface. On the samples of PLA composites without the addition of biomass (PLA 3251D), inoculated with molds, a slight increase was found (second degree), covering up to 25% of the tested surface.  
Figure 4: Intensity of mold fungi growth on the samples’ surfaces.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & \begin{tabular}{c} **Tensile Strength** \\ \(\delta_{\mathbf{M}}\) **(MPa)** \\ \end{tabular} & \begin{tabular}{c} **Tensile Modulus** \\ \(E_{\mathbf{t}}\) **(GPa)** \\ \end{tabular} & \
\begin{tabular}{c} **Flexural Strength** \\ \(\delta_{\mathbf{M}}\) **(MPa)** \\ \end{tabular} &
\begin{tabular}{c} **Flexural Modulus** \\ \(E_{\mathbf{t}}\) **(GPa)** \\ \end{tabular} \\ \hline PLA 3251D & \(65.5\pm 1.3\) & \(3.3\pm 0.2\) & \(105.4\pm 1.0\) & \(3.4\pm 0.1\) \\ PLA-FF-20 & \(55.6\pm 1.0\) & \(5.3\pm 0.3\) & \(89.2\pm 2.4\) & \(5.6\pm 0.2\) \\ PLA-DP-20 & \(54.2\pm 1.2\) & \(5.1\pm 0.3\) & \(85.7\pm 1.8\) & \(4.9\pm 0.3\) \\ PLA-LS-20 & \(53.1\pm 1.1\) & \(5.1\pm 0.3\) & \(84.4\pm 1.8\) & \(4.6\pm 0.2\) \\ \hline \hline \end{tabular}
\end{table}
Table 9: Tensile and flexural properties of PLA/flax composites.  
Composites not inoculated with molds (series S), both PLA-LS-20, PLA-DP-20 and PLA-FF-20 showed susceptibility to microorganisms other than test fungi in the second degree, which indicates the presence of substances that are a medium for the growth of microorganisms. The samples of biocomposites PLA-FF-20 were the most susceptible, and the PLA-LS-20 were the least susceptible; however, for all samples it was growth visible to the naked eye, covering up to 25% of the tested surface. At the same time, on samples of PLA composites without the addition of biomass (PLA 3251D), not inoculated, trace development of microorganisms other than test fungi was observed, visible only under a microscope.  
In addition, changes in the appearance of the tested samples were assessed. Discoloration of the tested samples of biocomposites containing flax biomass was found, whereas distortions and losses on the surface of the samples were not observed.  
The conducted microbiological tests showed a greater susceptibility of biocomposites containing flax biomass to the action of mold fungi, in relation to pure PLA. Moreover, in other studies, it was shown that the addition of lignocellulosic fillers, such as conifer bark or coniferous sawdust to PLA composites increased the susceptibility to the mold fungi fouling process [48]. The observed differences are related to the varieties of flax from which the biomass was obtained. Biocomposites PLA-FF-20 were the most susceptible to the test fungi, whereas biocomposites PLA-LS-20 were the most resistant to mold fungi. This may be due to the fact that lignification is much stronger in the stalks of linseed varieties than in the stalks of flax cultivated mainly for fiber.