# Evaluation of _Aspergillus flavus_ Growth on Weathered HDPE Plastics Contaminated with Diesel Fuel
## 3 Results
### Fungal Growth Dynamics on Plastic Substrates
#### 3.3.2 Comparison of Fungal Behavior at 25 \({}^{\circ}\)C by Plastic Matrix Type  
At 25 \({}^{\circ}\)C, the behavior of _Aspergillus flavus_ followed the same trend observed at 30 \({}^{\circ}\)C, although with a general reduction in colony growth and halo formation areas. The gray HDPE plastic contaminated and weathered for more than two years, as shown in Table 3, remained the most favorable substrate, with mean colony areas reaching up to 74.19 mm\({}^{2}\)\(\pm\) 25.08 and halo extensions up to 2623.59 mm\({}^{2}\). These results confirm that diesel weathering reduces its toxicity and enhances the fungus's metabolic activity, even at temperatures close to ambient.  
The white HDPE plastic contaminated with non-weathered diesel (less than two months of exposure), as presented in Table 3, again showed limited fungal growth, with mean colony areas ranging from 23.79 mm\({}^{2}\) to 38.17 mm\({}^{2}\), and halo formation being sporadic and highly variable (some exceeding 1000 mm\({}^{2}\), others completely absent). This heterogeneity suggests that the presence of fresh hydrocarbons and possibly plastic additives in the white HDPE continued to negatively impact fungal colonization.  
The control samples (uncontaminated gray HDPE), shown in Table 3, exhibited moderate and consistent growth. Colonies reached mean areas of up to 55.14 mm\({}^{2}\)\(\pm\) 13.24, with halos exceeding 1400 mm\({}^{2}\) in some replicates. While these values were lower than those observed at 30 \({}^{\circ}\)C, they indicate that the substrate supports active fungal metabolism even in the absence of hydrocarbons, confirming its suitability as an experimental reference baseline.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{**Weathered Samples**} & \multicolumn{2}{c}{**Unweathered Samples**} & \multicolumn{2}{c}{**Control Samples**} \\ \hline \multirow{2}{*}{**Sample G0 \({}^{\circ}\)C**} & **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 & 168.01 \(\pm\) 22.3 & 1647.17 \(\pm\) 463.91 & 11.72 \(\pm\) 4.12 & n.a. & 101.07 \(\pm\) 56.03 & n.a. \\
2 & 154.62 \(\pm\) 63.01 & 1632.86 \(\pm\) 470.5 & 18.54 \(\pm\) 9.16 & 257.85 \(\pm\) 311.29 & 108.89 \(\pm\) 61.16 & 1788.58 \(\pm\) 178.13 \\
3 & 275.51 \(\pm\) 30.16 & 2363.83 \(\pm\) 488.25 & 18.31 \(\pm\) 9.55 & 273.85 \(\pm\) 296.04 & 101.12 \(\pm\) 52.90 & 1951.67 \(\pm\) 426.44 \\
4 & 269.97 \(\pm\) 14.44 & 2347.39 \(\pm\) 580.89 & 18.31 \(\pm\) 9.55 & 273.85 \(\pm\) 296.04 & 103.15 \(\pm\) 41.69 & 2068.26 \(\pm\) 320.96 \\
5 & 355.8 \(\pm\) 125.13 & 2823.45 \(\pm\) 365.65 & 18.23 \(\pm\) 15.3 & 786.62 \(\pm\) 597.94 & 103.15 \(\pm\) 41.69 & 2068.26 \(\pm\) 320.96 \\
6 & 355.8 \(\pm\) 125.13 & 2823.45 \(\pm\) 365.65 & 20.1 \(\pm\) 14.16 & 1036.23 \(\pm\) 454.27 & 103.15 \(\pm\) 41.69 & 2290.89 \(\pm\) 698.34 \\  & Colony area & Halo area & Colony area & Halo area & Colony area & Halo area \\ \hline \end{tabular}
\end{table}
Table 2: 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 30 \({}^{\circ}\)C.