Recovery of Polyhydroxyalkanoates from Cooked Mussel Processing Wastewater at High Salinity and Acidic Conditions

Abstract

Polyhydroxyalkanoates (PHA) are biodegradable polymers that can be intracellularly produced by microorganisms valorizing organic-rich wastes. In the present study, a PHA production system was fed with mussel cooker wastewater after acidogenic fermentation. Besides low pH (4.0 ± 0.3) and high salt (21.7 ± 2.9 g NaCl/L) concentrations, this wastewater also contained nitrogen concentrations (0.8 ± 0.1 g N/L), which were previously reported to be a challenge to the PHA accumulating bacteria enrichment. Bacteria with a PHA storage capacity were selected in an enrichment sequencing batch reactor (SBR) after 60 days of operation. The enriched mixed microbial culture (MMC) was mainly formed by microorganisms from phylum Bacteroidetes, and genera Azoarcus, Comamonas and Thauera from phylum Proteobacteria. The MMC was able to accumulate up to 25 wt% of PHA that was mainly limited by the wastewater nitrogen content, which promoted biomass growth instead of PHA accumulation. Indeed, when the presence of nutrient was limited, PHA stored in the accumulation reactor increased to up to 40.9 wt%. This work demonstrated the feasibility of the enrichment of a MMC with a PHA storage ability valorizing the fish-canning industrial wastewater at low pH, which is generally difficult to treat in wastewater treatment plants.

Polyhydroxyalkanoates Production by Mixed Microbial Culture under High Salinity

“…However, the real feedstock used also had in the composition a small amount of ammonia and proteins that may have contributed to the slightly lower qPHAs values. The obtained values in the present study were also higher, as compared to a study by Alba Pedrouso et al, where the culture that had acclimatized at 5 g NaCl /L reached a qPHA of 0.24 Cmmol PHA /(Cmmol X .h) [21]. It was also considerably higher, as compared to the slowly adapted culture to 20 g NaCl /L in the work of Roibás-Rozas et al, where the qPHA was only 0.05 Cmmol PHA /(Cmmol X .h) [23].…”

“…Overall, Wen Q. et al suggested that osmotic stress may trigger the synthesis of PHA; however, at higher NaCl contents, bacteria consume PHAs in response to high osmotic stress, leading to a lower maximum PHA content [20]. Alba Pedrouso A. et al [21] were also able to obtain an MMC enriched in PHA-accumulating microorganisms at 5 g NaCl /L using real feedstock obtained from the acidogenic fermentation of cooked mussel processing wastewater. This culture was able to reach a PHA content of 25% wt.…”