Polyhydroxyalkanoates Production by Mixed Microbial Culture under High Salinity (original) (raw)
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The Science of the total environment, 2017
Polyhydroxyalkanoates (PHA) are biopolymers that can be an alternative against conventional plastics. The study reported herein evaluated the enrichment of a mixed microbial culture (MMC) operated under feast/famine regime and different pHs in a sequencing batch reactor (SBR) using acetate as sole carbon source to produce polyhydroxyalkanoates (PHAs). The enrichment step was evaluated at controlled pH of 7.5 and also without pH control (averaged value of 9.0). The acetate uptake rate (-qS) of both enrichments at the end of the experimental period exhibited similar behaviour being about 0.18CmolAcCmolX(-1)h(-1) and 0.19CmolAcCmolX(-1)h(-1) for SBR-A and SBR-B, respectively. However, the PHA-storing capacity of the biomass enriched without pH control was better, exhibiting a maximum PHA content of 36% (gPHAg(-1) VSS) with a PHA production rate (qPHA) of 0.16CmolPHACmolX(-1)h(-1). Batch experiments were performed to evaluate PHA-storing capacity of the enriched culture at different pHs...
Polyhydroxyalkanoates production alongside wastewater treatment by mixed microbial cultures /
2019
El enfoque de este trabajo de investigación es analizar el proceso de producción de polihidroxialcanoatos (PHA) en paralelo al tratamiento de aguas residuales. Los PHA se consideran sustitutos potenciales de los plásticos convencionales y dentro del concepto de economía circular, son considerados como productos de valor añadido. Sin embargo, los altos costos durante la producción, han limitado un uso extensivo de los PHA. En los últimos años se han invertido esfuerzos en el desarrollo de alternativas de bajo costo que mejoren el rendimiento del proceso reduzcan los precios de obtención. El proceso de producción de PHA que se evalúa en esta tesis incluye las siguientes etapas: 1. Fermentación acidogénica: Durante esta etapa se estudió el potencial de diferentes residuos para producir ácidos grasos volátiles (AGV) mediante fermentación acidogénica. El uso de residuos de bajo costo como sustratos para la producción de PHA, supone una disminución importante en el costo general del proce...
Sustainability
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 pr...
Industrial Crops and Products, 2016
Polyhydroxyalkanoates (PHA) are bacterial polyesters usually produced from costly sugars or volatile fatty acids (VFAs). In this work, two processing waters rich in vegetable proteins and reducing sugars, i.e. a mixture of saccharose and stachyose in Leguminous Processing Water (LPW) and a mixture of glucose and fructose in Fruit Processing Water (FPW), were tested as growth medium for PHA production in a two-stage fermentation with a unique marine bacterial species: Halomonas i4786. In preliminary shake flask experiments, it was shown that the two media can effectively support the bacterial growth and the accumulation of PHA (evaluated using Nile Red staining). In batch cultivation mode in a 5-L fermentor, PHA productivities of 1.6 g.L-1 and 1.8 g.L-1 were further achieved within 72h, in LPW and FPW respectively. Polymer characterization by Differential Scanning Calorimetry and Steric Exclusion Chromatography indicated that the two substrates led to the biosynthesis of polymers with different chain length, distribution and crystallinity. To summarize, these results show that by-products derived from local agri-food industry can be used as a user-adapted and cost-effective source to produce bio-sourced and biodegradable plastic materials.
Recovery of polyhydroxyalkanoates (PHAs) from wastewater: A review
Bioresource Technology, 2020
Polyhydroxyalkanoates (PHAs) are biopolyesters accumulated as carbon and energy storage materials under unbalanced growth conditions by various microorganisms. They are one of the most promising potential substitutes for conventional non-biodegradable plastics due to their similar physicochemical properties, but most important, its biodegradability. Production cost of PHAs is still a great barrier to extend its application at industrial scale. In order to reduce that cost, research is focusing on the use of several wastes as feedstock (such as agro-industrial and municipal organic waste and wastewater) in a platform based on mixed microbial cultures. This review provides a critical illustration of the state of the art of the most likely-to-be-scaleup PHA production processes using mixed microbial cultures platform and waste streams as feedstock, with a particular focus on both, upstream and downstream processes. Current pilot scale studies, future prospects, challenges and developments in the field are also highlighted.
Enrichment of a Mixed Bacterial Culture with a High Polyhydroxyalkanoate Storage Capacity
Biomacromolecules, 2009
Polyhydroxyalkanoates (PHAs) are microbial storage polymers that attract interest as bioplastics. PHAs can be produced with open mixed cultures if a suitable enrichment step based on the ecological role of PHA is used. An acetate-fed sequencing batch reactor operated with 1 day biomass residence time and with feast-famine cycles of 12 h was used to enrich a mixed culture of PHA producers. In subsequent fed-batch experiments under growth limiting conditions, the enriched mixed culture produced PHA up to a cellular content of 89 wt % within 7.6 h (average rate of 1.2 g/g/h). The PHA produced from acetate was the homopolymer polyhydroxybutyrate. The culture was dominated by a Gammaproteobacterium that showed little similarity on 16S rRNA level with known bacteria (<90% sequence similarity). The mixed culture process for PHA production does not require aseptic conditions. Waste streams rather than pure substrates could be used as raw materials.
POLYHYDROXYALKANOATES (PHAS) PRODUCTION FROM AEROBIC-MIXED CULTURES
This study assessed the optimal conditions for PHA production using saponified fatty acid, derived from sunflower oil (SO). A fed-batch reactor was used to produce PHA. A mixture of sewage and semi-treated oil palm effluent from a facultative pond was cultured for six months to obtain a steady-state condition. The culture was then transferred to the fed-batch system. SO mainly contains long-chain-fatty-acid (LCFA) with unsaturated fatty acid fractions of C 14:1 -C 18:3 , therefore the PHA production was assessed under feast-famine condition. The main purpose of supplementing saponified SO was to improve the production of PHA constituents (copolymer of hydroxyl-unit) such as hydroxybutyrates (HBs), hydroxyvalerates (HVs) and hydroxyhexanoates (HHs) in mixed cultures. Fed-batch operation under aerobic-mixed cultures increased the PHA production up to 33% of the dried cell. Although sludge submitted to aerobic condition in mixed cultures could improve the PHA production, the production rates are still low. This study found that the HBs constituent in the sludge is always higher compared to HVs and HHs. Saponified SO has high specific PHA storage rates (q p feast = 0.5 C-mol/C-mol. h) which are comparable to other vegetable oils (e.g. corn oil, soy bean oil, etc.) Abstrak: Kajian telah dijalankan bagi menilai keadaan optima penghasilan PHA menggunakan asid lemak tersaponifikasi yang diubahsuai daripada minyak bunga matahari (SO). Sebuah reaktor suapan-kelompok telah digunakan untuk menghasilkan PHA. Campuran daripada airsisa dan efluen separa olahan daripada kolam pengoksidaan dikulturkan selama enam bulan untuk menghasilkan keadaan 'steady-state'. Kultur tersebut kemudiannya dipindahkan ke sistem suapan-kelompok. SO mengandungi asid lemak rantaian panjang dalam kumpulan asid lemak tak tepu (C 14:1 -C 18:3 ), oleh itu penghasilan PHA telah diteliti semasa keadaan 'feast-famine'. Tujuan utama membekalkan SO yang tersaponifikasi adalah untuk menambah kualiti kandungan PHA (kopolimer unit hidroksil) seperti hidroksibutirat (HB), hidroksivalerat (HV) dan hidroksiheksanoat (HH) di dalam kultur campuran. Operasi suapan berkelompok menggunakan kultur campuran secara aerobik dapat meningkatkan penghasilan PHA sehingga 33% daripada Malaysian Journal of Civil Engineering 18(2) : 109-128 (2006) 110 berat sel kering. Walaupun enapcemar yang dikulturkan secara campuran dapat meningkatkan kualiti penghasilan PHA, kadarnya masih rendah. Kajian ini mendapati kandungan HB dalam enapcemar sentiasa lebih tinggi berbanding HV dan HH. SO yang tersaponifikasi mempunyai kadar simpanan spesifik PHA yang tinggi (q p feast = 0.5 C-mol/C-mol. h) dan setanding dengan minyak sayuran lain (seperti minyak jagung, minyak soya, dan sebagainya) Kata Kunci: Kultur Campuran Aerobik; Kondungan PHA; Asid Lemak Tersaponifikasi; Minyak Bunga Matahari.
Sustainability, 2022
In the context of circular economy and sustainable production of materials, this project investigated the feasibility of producing sustainable polyhydroxyalkanoates (PHA) from microalgae and sludge used in the treatment of municipal wastewater. The overall process was studied looking at the main steps: microalgae production, fermentation of the biomass, production and characterization of the PHAs. It was possible to obtain blends of hydroxybutyrate-hydroxyvalerate copolymers with high molecular weights and different compositions depending on the nature of the feedstock (mixed volatile fatty acids). In some cases, almost completely amorphous PHA materials were obtained, suggesting a potential diversification of uses and applications.
New Biotechnology, 2013
Please cite this article in press as: Villano, M. et al., Polyhydroxyalkanoates production with mixed microbial cultures: from culture selection to polymer recovery in a high-rate continuous process, New Biotechnol. (2013), http://dx.Polyhydroxyalkanoates (PHA) production with mixed microbial cultures (MMC) has been investigated by means of a sequential process involving three different stages, consisting of a lab-scale sequencing batch reactor for MMC selection, a PHA accumulation reactor and a polymer extraction reactor. All stages were performed under continuous operation for at least 4 months to check the overall process robustness as well as the related variability of polymer composition and properties. By operating both biological stages at high organic loads (8.5 and 29.1 gCOD/L d, respectively) with a synthetic mixture of acetic and propionic acid, it was possible to continuously produce PHA at 1.43 g/ L d with stable performance (overall, the storage yield was 0.13 COD/COD). To identify the optimal operating conditions of the extraction reactor, two digestion solutions have been tested, NaOH (1 M) and NaClO (5% active Cl 2 ). The latter resulted in the best performance both in terms of yield of polymer recovery (around 100%, w/w) and purity (more than 90% of PHA content in the residual solids, on a weight basis). In spite of the stable operating conditions and performance, a large variation was observed for the HV content, ranging between 4 and 20 (%, w/w) for daily samples after accumulation and between 9 and 13 (%, w/w) for weekly average samples after extraction and lyophilization. The molecular weight Q2 of the produced polymer ranged between 3.4 Â 10 5 and 5.4 Â 10 5 g/mol with a large polydispersity index. By contrast, TGA and DSC analysis showed that the thermal polymer behavior did not substantially change over time, although it was strongly affected by the extraction agent used (NaClO or NaOH).