Accumulation of polyhydroxyalkanoates by Microlunatus phosphovorus under various growth conditions |
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Authors: | Aygul Akar Esma Ucisik Akkaya S Koray Yesiladali Gamze Çelikyilmaz Emine Ubay Çokgor Candan Tamerler Derin Orhon Z Petek Çakar |
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Institution: | (1) Department of Molecular Biology and Genetics, Faculty of Science and Letters, Istanbul Technical University, Maslak, 34469, Istanbul, Turkey;(2) Department of Environmental Engineering, Faculty of Civil Engineering, Istanbul Technical University, Maslak, 34469, Istanbul, Turkey |
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Abstract: | Microlunatus phosphovorus is an activated-sludge bacterium with high levels of phosphorus-accumulating activity and phosphate uptake and release activities.
Thus, it is an interesting model organism to study biological phosphorus removal. However, there are no studies demonstrating
the polyhydroxyalkanoate (PHA) storage capability of M. phosphovorus, which is surprising for a polyphosphate-accumulating organism. This study investigates in detail the PHA storage behavior
of M. phosphovorus under different growth conditions and using different carbon sources. Pure culture studies in batch-growth systems were conducted
in shake-flasks and in a bioreactor, using chemically defined growth media with glucose as the sole carbon source. A batch-growth
system with anaerobic–aerobic cycles and varying concentrations of glucose or acetate as the sole carbon source, similar to
enhanced biological phosphorus removal processes, was also employed. The results of this study demonstrate for the first time
that M. phosphovorus produces significant amounts of PHAs under various growth conditions and with different carbon sources. When the PHA productions
of all cultivations were compared, poly(3-hydroxybutyrate) (PHB), the major PHA polymer, was produced at about 20–30% of the
cellular dry weight. The highest PHB production was observed as 1,421 mg/l in batch-growth systems with anaerobic–aerobic
cycles and at 4 g/l initial glucose concentration. In light of these key results regarding the growth physiology and PHA-production
capability of M. phosphovorus, it can be concluded that this organism could be a good candidate for microbial PHA production because of its advantages
of easy growth, high biomass and PHB yield on substrate and no significant production of fermentative byproducts. |
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Keywords: | Activated-sludge systems Microlunatus phosphovorus Polyhydroxyalkanoate Poly(3-hydroxybutyrate) Bacterial storage PHA PHB |
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