## 3 Results and Discussion
### Evaluation of PHA Production Processes Using CO2 as Feedback
\begin{table}
\begin{tabular}{l l l l l l l l l l l} \hline \hline
**Carbon Source Phase 1 Phase 2 Phase 3** & \(\mathbf{H_{2}O_{2}CO_{2}}\) **(**vol \(\%\)**)** & **CDM at Onset of Phase 2 (g/L)** & **CDM at Onset of Phase 2 (g/L)** & **CDM (g/L)** & **PHB (g/L)** & **PHB Content (\(\%\))** & **PHB Productivity (g/L/h)** & **Reference** \\ \hline Acetic acid & Acetic acid & Acetic acid & Acetic acid & - & 17 & 60 & 43 & 72 & 0.365 & This study \\ Acetic acid & Acetic acid & - & - & 15 & 40 & 30 & 75 & 0.257 & This study \\ Glycerol & CO\({}_{2}\) & - & 84.02.813.2 & 19 & 46 & 28 & 61 & 0.168 & [8] \\
**Protose** & **CO\({}_{2}\)** & - & **84.18.710.3** & **15** & **43** & **24** & **56** & **0.632** & [43] \\ Glucose & CO\({}_{2}\) & - & 84.02.813.2 & 13 & 38 & 24 & 63 & 0.108 & [5] \\
**CO\({}_{2}\)** & **CO\({}_{2}\)** & - & **62.010.1** & **10** & **30** & **22** & **75** & **0.314** & [44] \\
**Protose** & **CO\({}_{2}\)** & - & **83.03.510.6** & 10 & 27 & 15 & 56 & 0.237 & [43] \\ Glycerol & CO\({}_{2}\) & - & 84.02.813.2 & 10 & 18 & 13 & 72 & 0.187 & [5] \\
**CO\({}_{2}\)** & **CO\({}_{2}\)** & - & **60.2010** & **10** & **12** & **8** & **63** & **0.105** & [45] \\
**CO\({}_{2}\)** & **CO\({}_{2}\)** & - & **70.2010** & **10** & **16** & **6** & **38** & **0.150** & [46] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of PHB production in fed-batch fermentations of \(C\). _nocator_ at CDM between 10 and 20 g/L at the onset of nutrient limitation using CO\({}_{2}\) or acetic acid as carbon source and continuous stirred-tank reactor (CSTR) in decreasing order of final PHB concentration. Gas composition ratios that lie within the gas-explosion range (using lower explosion limit of 5.0 vol \(\%\) O\({}_{2}\)) are indicated in bold. \begin{table}
\begin{tabular}{l l l l l l l l l l l} \hline \hline
**Carbon Source Phase 1 Phase 2 Phase 3** & \(\mathbf{H_{2}O_{2}CO_{2}}\) **(**vol \(\%\)**)** & **CDM at Onset of** & **CDM** & **PHBV** & **fity** & **PHBV Content** & **PHBV Productivity** & **Reference** \\ \hline Acetic acid & Acetic acid & Acetic acid & Acetic acid & - & **Phase 2 (g/L)** & **(g/L)** & **(g/L)** & **(mol \%)** & **(\%)** & **(g/L/h)** & **Reference** \\ \hline Acetic acid & Acetic acid & Acetic-valeric acid & Acetic acid & - & 19 & 65 & 48 & 27 & 74 & 0.413 & This study \\ Glucose & CO\({}_{2}\)-valeric acid & - & 84.2813.2 & 15 & 32 & 25 & 72 & 78 & 0.480 & [10] \\
**CO\({}_{2}\)** & CO\({}_{2}\)-valeric acid & - & **60.2010** & **11** & **18** & **15** & **28** & **80** & **0.188** & [42] \\ CO\({}_{2}\) & CO\({}_{2}\)-valeric acid & - & NS\({}^{1}\) & NS & 7.3 & 6.5 & 42 & 90 & 0.135 & [47] \\
**CO\({}_{2}\)** & **CO\({}_{2}\)-valeric acid** & - & **77.7811.111.11** & **NS** & **NS** & **1.2** & **32** & **NS** & **0.005** & [48] \\
**CO\({}_{2}\)** & **CO\({}_{2}\)-valeric acid** & - & **70.2010** & NS & NS & NS & **64** & NS & NS & [49] \\ \hline \hline \end{tabular} \({}^{1}\) NS, not specified.  
\end{table} 
Table 5: Summary of PHB production in fed-batch fermentations of \(C\). _nocator_ using CO\({}_{2}\) or acetic acid as carbon source and continuous stirred-tank reactor (CSTR) in decreasing order of final PHB concentration. Gas composition ratios that lie within the gas-explosion range (using lower explosion limit of 5.0 vol \(\%\) O\({}_{2}\)) are indicated in bold.