![]() ), superoxide anion (O 2 −), and hydrogen peroxide (H 2O 2).coli strain (harboring the PHB synthesis genes) increases PHB production to protect cells from oxidative damage caused by reactive oxygen species (ROS) such as hydroxyl radicals (OH The knowledge of stress tolerance enhancements by PHB accumulation in microorganisms was further investigated by Goh et al. A third study that exposed knock out mutants of Burkholderia strains lacking essential genes for PHA production, to nutrient limitations, high osmotic pressure and high temperature showed lower survival compared to the wild-type. ![]() Another study using Aeromonas hydrophila suggested the enhancement of the survival ability of the strain by the simultaneous biosynthesis of PHA granules under various stress conditions. coli reported an increase in heat resistance with PHA production compared with the control strain. Cells with high PHB content had enhanced survival and tolerance toward heat challenge and oxidative stress. PHB is produced in native and engineered microorganisms by accumulating as granules in the cytoplasm in response to conditions of physiological stress. The bacteria utilize PHB when nutrients are limited through depolymerization into 3-hydroxybutyric acid (3HB) which is used to produce acyl-CoA and acetyl-CoA, that is metabolized in the tricarboxylic acid (TCA) cycle as a source of carbon and energy. In these microorganisms, it is synthesized from acetyl-CoA through the successive action of three enzymes, namely the β-ketoacyl-CoA thiolase ( phb A), the acetoacetyl-CoA reductase ( phb B) and the PHB polymerase ( phb C) that polymerizes acyl coenzyme A (acyl-CoA). PHB is a highly reduced carbon storage compound that serves as carbon and energy reserve in different microorganisms. The most common biodegradable plastic is poly(3-hydroxybutyrate) (PHB) that belongs to the family of polyhydroxyalkanoate (PHA). They are derived from inexpensive biomaterial, hence represent a sustainable and environmentally safe alternative to the synthetic petroleum-based polymers, which are introduced in substantial amounts into the ecosystem as residential and industrial waste products. The specificity of the source of PHB production is discussed, such as salinity, electricity, concurrent hydrogen production, and the possible involvement of reactive oxygen species (ROS).īiodegradable plastics are gaining wide interest. necator H16 as a biocatalyst only when the electrolysis was operated in the same solution. As a result, the PHB formation was detected with C. The overall PHB production efficiency was analyzed in reasonably short reaction cycles typically as short as 8 h. This setup allows to investigate the influence of different stress conditions, such as coexisting electrolysis, relatively high salinity, nutrient limitation, and starvation, on the production of PHB. In this study, we established an integrated one-pot electromicrobial setup in which carbon dioxide is reduced to formate electrochemically, followed by sequential microbial conversion into PHB, using the two model strains, Methylobacterium extorquens AM1 and Cupriavidus necator H16. The PHB belongs to the family of polyhydroxyalkanoate (PHA) that mostly accumulates as a granule in the cytoplasm of microorganisms to store carbon and energy. Poly(3-hydroxybutyrate) (PHB), a biodegradable polymer, can be produced by different microorganisms.
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