The mixture was digested at 70 C for 3 h, thus the PHA was dissolved in the chloroform. Once the samples reached room temperature, the remaining solids were filtered and the organic phase was collected in 3 ml of methanol.
PHA species dissolved in chloroform tend to precipitate in contact with methanol.Finally, the solid phase obtained was filtered through Whatman 0.45 lm membranes and weighted to calculate the percentage of PHA in the biomass expressed as total suspended solids (%, gPHA gTSS1).
The PHA accumulation yield (YPHA/COD) can be calculated as the ratio between the amount of PHA accumulated (gCOD L1) and the amount of VFA added (gCOD L1).
However, it can also be calculated considering the total amount of COD added, since the carbon source is not a pure mixture of VFA.
Although the non-VFA COD does not contribute to PHA storage, it is important for oxidation and biomass growth.
The oxidation yield (YOX/COD) was calculated from the area under the OUR area monitored during the accumulation batch, which corresponded to the amount of COD oxidised for catabolism. Finally, the growth yield (YX/COD) corresponded to the rest of the COD consumed.