Polyhydroxyalkanoates production from ethanol- and lactate-rich fermentate of confectionary industry effluents

Polyhydroxyalkanoate (PHA) production has been the focus of considerable research to increase productivities and reduce production costs. In this study, a fermented confectionary industry wastewater was used as feedstock for mixed microbial culture PHA production. The feedstock was dominated by lactate and ethanol (60-90 % of all soluble fermentation products). The culture selection reactor was inoculated with municipal activated sludge and was operated at an organic loading rate (OLR) of 100 Cmmol center dot L-1 center dot d-1, achieving a robust PHA-accumulating enrichment, which produced up to 52.6 +/- 0.4 wt% of PHA in accumulation assays. An OLR increase in the culture selection stage to 150 Cmmol center dot L-1 center dot d-1 led to a PHA content of 59.1 +/- 0.6, a yield of 0.93 +/- 0.01 Cmol-PHA center dot Cmol-S-1 and a productivity of 0.93 +/- 0.01 g-PHA L-1 center dot h-1. A correlation analysis of the impact of ethanol concentrations from 3.19 to 20.3 Cmmol center dot L-1 in the reactor showed that ethanol inhibited PHA production rate and yield and the consumption of other carbon sources available. Microbial community analysis revealed the increase of Amaricoccus genus during the bioreactor operation time, a known PHA accumulator. The produced polymer was poly(3-hydroxybutyrate) with an average molecular weight of 4.3 x 105 Da and a polydispersity index of 1.88.

Automated summary

The study focused on PHA production using fermented confectionary industry wastewater as feedstock. A mixed microbial culture with a high PHA content of up to 59.1 wt% was successfully enriched by operating a culture selection reactor at an organic loading rate of 150 Cmmol·L-1·d-1. Ethanol concentration was found to have an inhibitory effect on PHA production rate and yield. The produced polymer was poly(3-hydroxybutyrate) with a molecular weight of 4.3 x 105 Da and a polydispersity index of 1.88.