Polyhydroxyalkanoates production from fermented paperboard mill wastewater using acetate-enriched bacteria

The aim of the study was to investigate the use of dark fermented paperboard mill wastewater (PMW) containing volatile fatty acids for polyhydroxyalkanoates (PHA) production. Six sequencing batch reactors (SBRs) were initially fed with synthetic feed containing acetate and operated at different organic loading rates (OLRs) of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 gCOD l⁻¹ day⁻¹ for PHA-storing bacteria enrichment. The maximum PHA content and yield (Y _PHA/S) were 67.44 ± 5.88 % and 0.45 ± 0.39 C-mol C-mol⁻¹ at OLR of 1.5 gCOD l⁻¹ day⁻¹, respectively. The synthetic feed was replaced by dark fermented PMW effluent rich in acetate, butyrate, propionate, and lactate at the accumulation stage resulting in a PHA content and yield of 58.57 ± 4.02 % and 0.46 ± 0.09 C-mol C-mol⁻¹, respectively. The maximum specific PHA production rate (q _PHA ^max ) amounted to 0.29 ± 0.1 C-mol C-mol⁻¹ X⁻¹ h⁻¹. Illumina MiSeq sequencing of bacterial 16S rRNA gene showed that Proteobacteria and Bacteroidetes increased from 37.4 to 77.6 % and from 2.49 to 17.66 % at enrichment and accumulation stages, respectively. Actinobacteria (15.44 %), Chloroflexi (8.15 %), Planctomycetes (7.46 %), and Acidobacteria (6.0 %) were detected at the enrichment SBRs.