# Evaluation of _Aspergillus flavus_ Growth on Weathered HDPE Plastics Contaminated with Diesel Fuel
## 3 Results
### Fungal Growth Dynamics on Plastic Substrates
#### 3.3.3 Comparison of Fungal Behavior at 20 \({}^{\circ}\)C  
At 20 \({}^{\circ}\)C, the behavior of _Aspergillus flavus_ followed the same pattern observed at higher temperatures, although with an overall reduction in mycelial growth rate and halo formation. The weathered and diesel-contaminated gray plastic (see Table 4) remained the most favorable matrix, reaching an average colony area of 78.39 mm\({}^{2}\)\(\pm\) 23.36 and halo areas up to 1640.63 mm\({}^{2}\)\(\pm\) 1044.26. Although these figures were lower than those observed at 25 \({}^{\circ}\)C and 30 \({}^{\circ}\)C, they confirm that the weathered contaminant continues to offer conditions compatible with fungal activity, even under less favorable thermal conditions. The unweathered, diesel-contaminated white plastic (see Table 4) once again showed the most limited growth. Average colony areas ranged from 19.24 mm\({}^{2}\) to 33.85 mm\({}^{2}\), with halos absent in several replicates or very small, with maximum values around 871.23 mm\({}^{2}\). The data dispersion and limited halo formation reinforce the hypothesis that both the composition of commercial diesel and the additives present in white HDPE negatively impact _A. flavus_ colonization capacity. In the case of the control (uncontaminated gray plastic, see Table 4), fungal growth was moderate and relatively homogeneous, with average colony areas of 42.30 mm\({}^{2}\)\(\pm\) 24.32 and halo areas reaching up to 1538.96 mm\({}^{2}\)\(\pm\) 949.21. Although these values were lower than those recorded at higher temperatures, they indicate that the fungus maintains a stable growth capacity, confirming the utility of this matrix as a comparative reference under varying thermal conditions. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multicolumn{3}{c}{**Weathered Samples**} & \multicolumn{2}{c}{**Unweathered Samples**} & \multicolumn{2}{c}{**Control Samples**} \\ \hline \multirow{2}{*}{**Sample (20 \({}^{\circ}\)C)**} & **Mean \(\pm\) SD** & **Mean \(\pm\) SD** & **Mean \(\pm\) SD** & **Mean \(\pm\) SD** & **Mean \(\pm\) SD** & **Mean \(\pm\) SD** \\  & **(mm\({}^{2}\))** & **(mm\({}^{2}\))** & **(mm\({}^{2}\))** & **(mm\({}^{2}\))** & **(mm\({}^{2}\))** & **(mm\({}^{2}\))** \\ \hline
1 & 29.31 \(\pm\) 7.82 & 314.65 \(\pm\) 173.9 & 14.78 \(\pm\) 10.97 & n.a. & 24.24 \(\pm\) 10.51 & n.a. \\
2 & 119.42 \(\pm\) 56.37 & 735.88 \(\pm\) 428.1 & 33.92 \(\pm\) 20.04 & 157.17 \(\pm\) 133.89 & 69.55 \(\pm\) 26.68 & 1024.85 \(\pm\) 86.90 \\
3 & 90.86 \(\pm\) 52.75 & 625.89 \(\pm\) 343.95 & 53.27 \(\pm\) 30.78 & n.a. & 69.55 \(\pm\) 26.68 & 1024.85 \(\pm\) 86.90 \\
4 & 78.39 \(\pm\) 23.36 & 660.4 \(\pm\) 152.58 & 54.29 \(\pm\) 29.05 & n.a. & 128.11 \(\pm\) 100.07 & 1568.5 \(\pm\) 570.31 \\
5 & 78.39 \(\pm\) 23.36 & 660.4 \(\pm\) 152.58 & 46.59 \(\pm\) 24.28 & 498.91 \(\pm\) 174.39 & 95.48 \(\pm\) 34.63 & 1896.73 \(\pm\) 248.84 \\
6 & 78.39 \(\pm\) 23.36 & 660.4 \(\pm\) 152.58 & 47.68 \(\pm\) 22.43 & 526.83 \(\pm\) 134.9 & 99.47 \(\pm\) 33.99 & 1987.47 \(\pm\) 174.92 \\  & Colony area & Halo area & Colony area & Halo area & Colony area & Halo area \\ \hline \end{tabular}
\end{table} 
Table 4: Total colony and halo areas on samples of weathered HDPE gray plastic contaminated with diesel fuel (weathered samples), unweathered white HDPE plastic contaminated with diesel fuel (unweathered samples) and unweathered and uncontaminated gray HDPE plastic samples (control samples), incubated at 20 \({}^{\circ}\)C.