No abstract

No abstract

No abstract

No abstract

Polyhydroxyalkanoates (PHA) are biopolymers with potential to replace conventional oil-based plastics. However, PHA high production costs limit their scope of commercial applications. Downstream processing is currently the major cost factor for PHA production but one of the least investigated aspects of the PHA production chain. In this study, the extraction of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) produced at pilot scale by a mixed microbial culture was performed using sodium hydroxide (NaOH) or sodium hypochlorite (NaClO) as digestion agents of non-PHA cellular mass. Optimal conditions for digestion with NaOH (0.3 M, 4.8 h) and NaClO (9.0%, 3.4 h) resulted in polymers with a PHA purity and recovery of ca. 100%, in the case of the former and ca. 99% and 90%, respectively, in the case of the latter. These methods presented higher PHA recoveries than extraction by soxhlet with chloroform, the benchmark protocol for PHA extraction. The polymers extracted by the three methods presented similar PHA purities, molecular weights and polydispersity indices. Using the optimized conditions for NaOH and NaClO digestions, this study analyzed the effect of the initial intracellular PHA content (40–70%), biomass concentration (20–100 g/L) and biomass pre-treatment (fresh vs. dried vs. lyophilized) on the performance of PHA extraction by these two methods.

No abstract

This study focused on the biodegradation of an azo dye (Acid Red 14, AR14) in two anaerobic−aerobic sequencing batch reactors (SBRs) treating synthetic textile wastewater, operated with aerobic granular sludge under different hydrodynamic regimens. The aim was to investigate the fate of the anaerobic AR14 breakdown products (aromatic amines) during the SBRs' aerobic reaction phase. Specifically, liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) was used for structural characterization of AR14 biodegradation metabolites, their molecular formulas being confirmed by accurate mass measurements. Nineteen molecules potentially related to AR14 were detected in the SBRs, and their relative abundances were followed along the aerobic stage of treatment cycles. The two SBRs shared most of the identified compounds but with differences in their metabolite profiles. Biodecolorization through AR14 anaerobic azo bond reduction was confirmed by the identification of the aromatic amine 4-amino-naphthalene-1-sulfonic acid, which was further aerobically biodegraded, involving deamination and hydroxylation of the aromatic ring. The other aromatic amine (1-naphthol-2-amino-4sulfonic acid) was not detected, being suggested to undergo autoxidation reactions forming dimeric, stable products. A different AR14 biodegradation pathway was observed when nitrate was added to the feed, a new intermediate product being detected (naphthalene-1-sulfonate).

Treatment of the highly polluting and variable textile industry wastewater using aerobic granular sludge (AGS) sequencing batch reactors (SBRs) has been recently suggested. Aiming to develop this technology application, two feeding strategies were compared regarding the capacity of anaerobic-aerobic SBRs to deal with disturbances in the composition of the simulated textile wastewater feed. Both a statically fed, anaerobic-aerobic SBR and an anaerobic plug-flow fed, anaerobic-aerobic SBR could cope with shocks of high azo dye concentration and organic load, the overall chemical oxygen demand and color removal yields being rapidly restored to 80%. Yet, subsequent azo dye metabolite bioconversion was not observed, along the 315-day run. Moreover, switching from a starch-based substrate to acetate in the feed composition deteriorated AGS stability. Overall, the plug-flow fed SBR recovered more rapidly from the imposed disturbances. Further research is needed towards guaranteeing long-term AGS stability during the treatment of textile wastewater.