How temperature shapes the biosynthesis of polyhydroxyalkanoates in mixed microbial cultures. 2023

Tania Palmeiro-Sánchez, and Alison Graham, and Piet Lens, and Vincent O'Flaherty
Department of Microbiology, College of Science and Engineering and Ryan Institute, University of Galway, Galway, Ireland.

Three sequential batch reactors were operated for the enrichment in microbial communities able to store polyhydroxyalkanoates (PHAs) using activated sludge as inoculum. They ran simultaneously under the same operational conditions (organic loading rate, hydraulic and solids retention time, cycle length, C/N ratio) just with the solely difference of the working temperature: psychrophilic (15°C), mesophilic (30°C), and thermophilic (48°C). The microbial communities enriched showed different behaviors in terms of consumption and production rates. In terms of PHA accumulation, the psychrophilic community was able to accumulate an average amount of 17.7 ± 5.7 wt% poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), the mesophilic 40.3 ± 7.0 wt% PHBV, and the thermophilic 14.8 ± 0.3 wt% PHBV in dry weight over total solids. The average PHBV production yields for each selected community were 0.41 ± 0.12 CmmolPHBV /CmmolVFA at 15°C, 0.64 ± 0.05 CmmolPHBV /CmmolVFA at 30°C, and 0.39 ± 0.14 CmmolPHBV /CmmolVFA at 48°C. The overall performance of the mesophilic reactor was better than the other two, and the copolymers obtained at this temperature contained a higher PHV fraction. The physico-chemical properties of the obtained biopolymers at each temperature were also measured, and major differences were found in the molecular weight, following an increasing trend with temperature. PRACTITIONER POINTS: PHBV molecular weight is influenced by the operational temperature increasing with it. Increasing temperatures promote the production of HB over HV. The best accumulation performance was found at 30°C for the tested operational conditions.

UI MeSH Term Description Entries
D006885 Hydroxybutyrates Salts and esters of hydroxybutyric acid. Hydroxybutyric Acid Derivatives,Hydroxybutyric Acids,Acid Derivatives, Hydroxybutyric
D013696 Temperature The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms. Temperatures
D054813 Polyhydroxyalkanoates Biodegradable microbial polyesters which contain hydroxyacyl monomers. Polyhydroxyalkanoates are carbon and energy reserve materials produced and sequestered in cytoplasmic granules called polyhydroxyalkanoate or PHA granules by various archaea and bacteria and may additionally provide protective mechanism to the microbes. They are biosynthesized by microbial polyhydroxyalkanoate synthase enzymes using fatty acids or citramalate synthase enzymes using glucose. Poly(hydroxyalkanoate),Poly(hydroxyalkanoates),Polyhydroxyalkanoate
D019149 Bioreactors Tools or devices for generating products using the synthetic or chemical conversion capacity of a biological system. They can be classical fermentors, cell culture perfusion systems, or enzyme bioreactors. For production of proteins or enzymes, recombinant microorganisms such as bacteria, mammalian cells, or insect or plant cells are usually chosen. Fermentors,Bioreactor,Fermentor

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