## 3 Results
### Bacteria Growth  
The growth of _C. necator_ in nitrogen rich TSB and in nitrogen low media (BSM) was conducted over a 48 h period with and without PS0-4 for comparison (Figure 6). From a 25 mL starter flask of _C. necator_ grown in TSB (48 h at 30 \({}^{\circ}\)C at 150 rpm), 1 mL of inoculum was pipetted into each conical flask with 250 mL of media (TSB/BSM) to ensure relatively close starting point numbers (log 10 CFU mL\({}^{-1}\)) of bacterial fermentations. The nitrogen limited (BSM) fermentations did not yield PHAs and cell numbers were merely maintained with a maximum dry biomass of 0.16 g/L. The initial cell numbers of all cultures were 7.8 \(\pm\) 0.2 log10 CFU mL\({}^{-1}\). A two-way multiple ANOVA and Turkey's multiple comparison confirmed there was no significance between BSM and BSM + PS0 CFU numbers (_P_ = 0.37), indicating that PS0 alone is not enough for increased biomass. With TSB (nitrogen rich medium) a maximum cell number of 10.0 \(\pm\) 0.8 log10 CFU mL\({}^{-1}\) was obtained (Figure 6a). This represents an increase in the log10 CFU mL\({}^{-1}\) number of approximately 2.2 log10 CFU mL\({}^{-1}\) across all nitrogen rich cultures. The results showed there was also no significance with PS4 and TSB (_P_ = 0.76), and although the dry biomass recovered was 0.99 g, after further analysis, it was found that this sample contained low molecular mass (8000 Da) PS4 particles that passed through the extraction process, giving inaccurate results. This adjusted P value also suggests that PS4 was not metabolized and that the conditions (180 \({}^{\circ}\)C, O\({}_{3}\)/O\({}_{2}\) for 20 h) used to produce PS4 (a powder  
Figure 5: Full stacked proton decoupled \({}^{13}\)C-NMR spectra of the PS0 (original) and PS1–4 (thermally treated) samples (**a**) and (**b**) expansions of the backbone methylene/methine (**c**) and _ipso_ carbon regions \({}^{1}\)H-NMR spectra of the PS1–4 (thermally treated) samples. Labels 1–6 indicate the carbon atoms on the PS diagram featured. rather than a flake) may have been too extreme to produce a viable carbon source, despite the average molecular mass being the lowest. The relatively dense, smaller PS4 particles were highly stable, crystalline, possessed low hydrophilic (AN = 23.6) properties, and were less structurally open as they are most likely in aromatic arrangements in comparison to the higher molecular mass PS flakes [47]. All other comparisons of PS0 and PS1-4 with TSB media against BSM fermentations showed significant results, including PS0 + TSB and TSB with a significance of \(P\) = 0.017, indicating that the addition of PS in either treated form increases cell numbers. Moreover, comparisons of PS1, PS2, and PS3 (the successfully oxidized prodegraded PS specimens) against BSM (Figure 6b) showed the greatest significance (\(P\) = 0.001) and they also yielded the highest dry biomass and PHA yields. The average cell dry weight (CDW) and the average PHA yield in grams per liter of fermentation media is presented in Table 4.  
The cell growth analysis showed that prodegraded PS in TSB or BSM does not have a negative effect on the growth of _C. necator._ Previous experiments have shown that certain plastics, such as polyethylene (PE), have negligible antimicrobial properties against both gram positive and gram negative bacteria [48; 49; 35]. The low antimicrobial activity of some plastics could be due to the absence of antimicrobial moieties, such as chlorine or fluorine, within the polymer chains, which could be released during an oxidation process. They could then leach out into the surrounding media [50]. However, PS is considered relatively stable and it is widely thought of as a safe plastic for food and drink packaging.