Exploiting olive oil mill effluents as a renewable resource for production of biodegradable polymers through a combined anaerobic–aerobic process

TLDR

The study evaluates a three‑stage anaerobic–aerobic process for producing polyhydroxyalkanoates from olive oil mill effluents. The process comprises (1) anaerobic packed‑bed biofilm fermentation of OME to volatile fatty acids, (2) aerobic sequencing‑batch reactor enrichment of PHA‑storing mixed cultures, and (3) aerobic batch operation to harvest the stored PHAs. Anaerobic fermentation raised VFA content from 18 % to ~32 % COD, the SBR enriched high‑storage biomass comparable to synthetic VFA, DGGE revealed distinct bacterial strains, and the final batch stage produced PHAs whose concentration rose linearly with load, with roughly half derived from alcohols rather than VFAs, demonstrating effective simultaneous treatment and valorization. © 2009 Society of Chemical Industry.

Abstract

Abstract BACKGROUND: The performance of a three‐stage process for polyhydroxyalkanoate (PHA) bioproduction from olive oil mill effluents (OME) has been investigated. In the first anaerobic stage OME were fermented in a packed bed biofilm reactor into volatile fatty acids (VFAs). This VFA‐rich effluent was fed to the second stage, operated in an aerobic sequencing batch reactor (SBR), to enrich mixed cultures able to store PHAs. Finally, the storage response of the selected consortia was exploited in the third aerobic stage, operated in batch conditions. RESULTS: The anaerobic stage increased the VFA percentage in the OME from 18% to ∼32% of the overall chemical oxygen demand (COD). A biomass with high storage response was successfully enriched in the SBR fed with the fermented OME at an organic load rate of 8.5 gCOD L −1 d −1 , with maximum storage rate and yield (146 mgCOD gCOD −1 h −1 and 0.36 COD COD −1 , respectively) very similar to those obtained with a synthetic VFA mixture. By means of denaturing gradient gel electrophoresis (DGGE) analysis, different bacterial strains were identified during the two SBR runs: Lampropedia hyalina and Candidatus Meganema perideroedes , with the synthetic feed or the fermented OMEs, respectively. In the third stage, operated at increasing loads, the maximum concentration of the PHA produced increased linearly with the substrate fed. Moreover, about half of the stored PHAs were produced from substrates other than VFAs, mostly alcohols. CONCLUSION: The results obtained indicate that the process is effective for simultaneous treatment of OME and their valorization as a renewable resource for PHA production. Copyright © 2009 Society of Chemical Industry