Production and Characterization of Polyhydroxyalkanoates from Wastewater via Mixed Microbial Cultures and Microalgae (original) (raw)
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Environmental technology, 2017
In this study, seven strains of bacteria with polyhydroxyalkanoates (PHA)-producing ability (i.e. Bacillus cereus, Pseudomonas putida, Bacillus pumilus, Pseudomona huttiensis, Yersinia frederiksenii, Aeromonas ichthiosmia, and Sphingopyxis terrae) were isolated from various waste treatment plants in Hong Kong. Simultaneous wastewater treatment and PHA accumulation were successfully achieved in the bioreactors using isolated bacteria from different sludges. At the organic loading less than 13,000 ppm, more than 95% of chemical oxygen demand (COD) was removed by the isolated strains before the decrease of PHA accumulation. In addition, more than 95% of nitrogen removal was achieved by all isolated strains. In the bioreactors inoculated with single strains, the highest yields of poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxyvalerate) (PHV) were obtained in A. ichthiosmia (84 mg PHB/g) and B. cereus (69 mg/g), respectively. For the mixed culture, the highest yields of PHB and PHV were...
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.
Biochemical Engineering Journal, 2016
Polyhydroxyalkanoates (PHAs) are bioplastics that naturally accumulate in the microbial cells while performing organic substrate metabolism. PHAs bioconversion in microbial cells is affected by both growth environments (aerobic and anaerobic) and feeding systems (carbon and nutrient limitations). Sequential batch reactors (SBRs) were used in this research for producing PHAs; studies showed on an average 42% with a maximum of 63% PHAs yield under anaerobic-oxic conditions quantified by gas chromatography. Produced PHAs from phase 4 were thermally and physically characterized. Fourier transform infrared spectroscopy showed strong presence of carbonyl peaks at 1720 cm-1 in all PHAs. Gel permeation chromatography reported polydipersity index values in range of 2.4 to 3.6 showing nonuniformity of molecular weights in the slice of PHAs and differential scanning calorimetry reported melting point temperatures of 146 to 154 o C, confirming usefulness of produced PHAs in industrial applications. X-Ray Diffraction confirmed crystal structure in all PHAs with the most crystalline from SBR3. Thermogravimetric analysis further confirmed highest thermal degradation temperature of 283 o C for PHAs from SBR3. Different blends of wastewater fed to mixed sodium acetate acclimatized biomass further showed the importance of substrate carbon source for PHAs production in various growth environments.
Producing microbial polyhydroxyalkanoate (PHA) biopolyesters in a sustainable manner
A B S T R A C T Sustainable production of microbial polyhydroxyalkanoate (PHA) biopolyesters on a larger scale has to consider the " four magic e " : economic, ethical, environmental, and engineering aspects. Moreover, sustainability of PHA production can be quantified by modern tools of Life Cycle Assessment. Economic issues are to a large extent affected by the applied production mode, downstream processing, and, most of all, by the selection of carbon-rich raw materials as feedstocks for PHA production by safe and naturally occurring wild type microorganisms. In order to comply with ethics, such raw materials should be used which do not interfere with human nutrition and animal feed supply chains, and shall be convertible towards accessible carbon feedstocks by simple methods of upstream processing. Examples were identified in carbon-rich waste materials from various industrial braches closely connected to food production. Therefore, the article shines a light on hetero-, mixo-, and autotrophic PHA production based on various industrial residues from different branches. Emphasis is devoted to the integration of PHA-production based on selected raw materials into the holistic patterns of sustainability; this encompasses the choice of new, powerful microbial production strains, non-hazardous, environmentally benign methods for PHA recovery, and reutilization of waste streams from the PHA production process itself.
Synthesis of Polyhydroxyalkanoates in Municipal Wastewater Treatment
2000
Biologically derived polyesters known as polyhydroxyal- kanoates (PHAs) represent a potentially ''sustainable'' replacement to fossil- fuel-based thermoplastics. However, current commercial practices that produce PHA with pure microbial cultures grown on renewable, but refined, feedstocks (i.e., glucose) under sterile conditions do not represent a sustain- able commodity. Here, we report on PHA production with a mixed microbial consortium indigenous to an
Bioresource Technology, 2012
Production of biodegradable plastics in the form of polyhydroxyalkanoates (PHA) especially from renewable substrates is gaining interest. The present work mainly aims to investigate the influence of substrate load and nutrient concentration (nitrogen and phosphorous) on PHA production using wastewater as substrate and mixed culture as biocatalyst. PHA accumulation was high at higher substrate load [OLR3, 40.3% of dry cell weight (DCW)], low nitrogen (N 1 , 45.1% DCW) and low phosphorous (P 1 , 54.2% DCW) conditions. With optimized nutrient conditions production efficiency increased by 14%. Fractional composition of PHA showed co-polymer [poly(b-OH) butyrate-co-poly(b-OH) valerate, P3(HB-co-HV)] contains PHB (88%) in more concentration compared to PHV (8%). Dehydrogenase and phosphatase enzymatic activities were monitored during process operation. Good substrate degradation (as COD) of 75% was registered during PHA production. The phylogenetic profile of 16S rRNA sequencing showed the dominance of Firmicutes (71.4%) and Proteobacteria (28.6%), which are known to involve in PHA accumulation and waste treatment.
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.
Biotechnology for Biofuels
Background: In Europe, almost 87.6 million tonnes of food waste are produced. Despite the high biological value of food waste, traditional management solutions do not consider it as a precious resource. Many studies have reported the use of food waste for the production of high added value molecules. Polyhydroxyalkanoates (PHAs) represent a class of interesting bio-polyesters accumulated by different bacterial cells, and has been proposed for production from the organic fraction of municipal solid waste (OFMSW). Nevertheless, until now, no attention has been paid to the entire biological process leading to the transformation of food waste to organic acids (OA) and then to PHA, getting high PHA yield per food waste unit. In particular, the acid-generating process needs to be optimized, maximizing OA production from OFMSW. To do so, a pilot-scale Anaerobic Percolation Biocell Reactor (100 L in volume) was used to produce an OA-rich percolate from OFMSW which was used subsequently to produce PHA. Results: The optimized acidogenic process resulted in an OA production of 151 g kg −1 from fresh OFMSW. The subsequent optimization of PHA production from OA gave a PHA production, on average, of 223 ± 28 g kg −1 total OA fed. Total mass balance indicated, for the best case studied, a PHA production per OFMSW weight unit of 33.22 ± 4.2 g kg −1 from fresh OFMSW, corresponding to 114.4 ± 14.5 g kg −1 of total solids from OFMSW. PHA composition revealed a hydroxybutyrate/hydroxyvalerate (%) ratio of 53/47 and Mw of 8•10 5 kDa with a low polydispersity index, i.e. 1.4. Conclusions: This work showed how by optimizing acidic fermentation it could be possible to get a large amount of OA from OFMSW to be then transformed into PHA. This step is important as it greatly affects the total final PHA yield. Data obtained in this work can be useful as the starting point for considering the economic feasibility of PHA production from OFMSW by using mixed culture.
Proceedings of the National Academy of Sciences, India Section B: Biological Sciences, 2015
Municipal sewage triggers a stress prone environment to accumulate polyhydroxyalkanoates (PHAs) in the cytosol of bacteria. In view of that, different Bacillus species were isolated from municipal sewage and screened for evaluating their efficacy of PHA production. Growth parameters such as temperature, pH, glucose concentration and carbon nitrogen combinations were optimized with respect to higher biomass production as it is analogous to PHA accumulation. Under optimized conditions, the Bacillus species produced 3.09 g/L of PHAs which was estimated as a higher yield in comparison to other similar strains. Fourier transform infrared spectroscopic analysis of the extracted polyhydroxybutyrate confirmed the distinct peak corresponding to C=O group, whereas proton nuclear magnetic resonance (1 H NMR) and differential scanning colorimetric analysis exhibited detailed insight of its chemical structure and properties by reflecting monomeric unit. The high yielding bacterial isolate was identified by 16S rDNA sequencing and the sequence was confirmed as Bacillus subtilis with an accession no. KP172548 after submission to NCBI data base. The potential bacterium may be further exploited for cost effective and mass scale production of biopolymer.