## Results
### Culture's Dynamic Performance
Consequently, the culture was truly subjected to the selective pressure of least and famine regime, which enhanced the PHA-accumulating organisms' proliferation. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Periods** & **I** & **II** & **III** & **IV** & **V** \\ \hline \multicolumn{5}{l}{**Selection Performance Parameters**} \\ \hline
**APHA** (wt.\%) & 22 (1) & 22 (3) & 12 (1) & 5 (1) & 2 (1) \\
**YHA** (Cmol-PHA-Cmol-HOrgs\({}^{-1}\)) & 0.50 (0.05) & 0.55 (0.06) & 0.35 (0.04) & 0.23 (0.05) & 0.06 (0.02) \\
**qHA** (Cmol-PHA-Cmol-X\({}^{-1}\).h\({}^{-1}\)) & 0.18 (0.01) & 0.17 (0.02) & 0.07 (0.01) & 0.05 (0.01) & 0.01 (0.00) \\
**-qHOrgs** (Cmol-HOrgs-Cmol-X\({}^{-1}\).h\({}^{-1}\)) & 0.37 (0.03) & 0.24 (0.02) & 0.20 (0.01) & 0.12 (0.02) & 0.18 (0.13) \\
**-qProt** (mgProt-gX\({}^{-1}\).h\({}^{-1}\)) & 6.2 (1.5) & 6.4 (2.1) & 11.6 (2.0) & 11.6 (2.4) & 16.7 (1.2) \\
**\(\Delta\)Prot** (mgProt-cycle\({}^{-1}\)) & 27.7 (0.2) & 32.5 (3.0) & 48.5 (2.3) & 76.2 (2.0) & 79.7 (1.4) \\ \hline \multicolumn{5}{l}{**Accumulation Performance Parameters**} \\ \hline
**APHA** (wt.\%) & 43 & 31 & 14 & - & - \\
**PHA composition** & 89/11 & 92/8 & 92/8 & - & - \\
**(wt.\%HB/wt.\%HV)** & & & & & \\
**YHA** (Cmol-PHA-Cmol-HOrgs\({}^{-1}\)) & 0.85 (0.12) & 0.76 (0.13) & 0.52 (0.07) & - & - \\
**qHA** (Cmol-PHA-Cmol-X\({}^{-1}\) & 0.17 (0.02) & 0.18 (0.03) & 0.11 (0.00) & - & - \\
**h\({}^{-1}\))** & & & & & \\
**Productivity** & & & & & \\ (gPHA-L\({}^{-1}\).h\({}^{-1}\)) & 0.20 & 0.25 & 0.12 & - & - \\ \hline \multicolumn{5}{l}{The listed values are averages (Selection Performance Parameters) or calculated values (Accumulation Performance Parameters) and associated standard errors of the mean (SEM), in brackets. Nr. of measurements: (I.5; II.6; II.6; IV.5; V.7).} \\ \end{tabular}
\end{table} 
Table 3: The average performance of the enriched MMC in the selection reactor in the five different periods (I–V); and an overview of the PHA-accumulation assays with the MMC selected on Periods I, II, and III. The specific PHA production rates observed in Periods I and II (0.18 and 0.17 Cmol-PHA\(\cdot\)Cmol-X\({}^{-1}\).h\({}^{-1}\), respectively), were in the range, or higher, than those reported in the literature for similar systems, operated with different fermented feedstocks (0.05-0.11 Cmol-PHA\(\cdot\)Cmol-X\({}^{-1}\).h\({}^{-1}\) obtained with fermented molasses [33], and 0.06 Cmol-PHA\(\cdot\)Cmol-X\({}^{-1}\).h\({}^{-1}\) with fermented paper mill effluent [3]). However, the obtained values were slightly lower than the maximum values, previously obtained, with fCW by [PERSON] et al. [15], 0.27 Cmol-PHA\(\cdot\)Cmol-X\({}^{-1}\).h\({}^{-1}\). This difference might be related, either to the different OLRs applied (54.4 and 43.0 Cmmol-L\({}^{-1}\).d\({}^{-1}\) in [PERSON] et al. and in the present study, respectively), or to the different organic acids composition. Nevertheless, both cultures selected in Periods I and II showed good and similar storing-capacities during the accumulation tests, reaching storage yields of 0.85 and 0.76, and PHA productivities of 0.20 and 0.25 gPHA\(\cdot\)L\({}^{-1}\).h\({}^{-1}\), respectively (Table 3). The decrease of nitrogen supplementation to a quarter of the reference (Period II to III), resulted in immediate perturbations in the biomass concentration and, consequently, in the F/f ratio (Figure 1). The biomass concentration decreased after the perturbation, and it did not recover, stabilising in a slightly lower value than that observed in the previous period (1.3 \(\pm\) 0.1 and 1.7 \(\pm\) 0.1 gVSS\(\cdot\)L\({}^{-1}\) in Periods III and II, respectively). The achieved biomass concentration was twice that supported by the supplied ammonia (estimated value of 0.6 gVSS\(\cdot\)L\({}^{-1}\), Figure 1), indicating a larger amount of nitrogen was obtained from proteins (protein consumed per cycle increased to 48.5 mg, Table 3). The F/f ratio increased consistently, up to 0.8, during the initial six days, but it did partially recover eight days after the perturbation was imposed.