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    Öğe
    Investigation of the Physiology of the Obligate Alkaliphilic Bacillus marmarensis GMBE 72T Considering Its Alkaline Adaptation Mechanism for Poly(3-hydroxybutyrate) Synthesis
    (Mdpi, 2021) Atakav, Yagmur; Pinar, Orkun; Kazan, Dilek
    The novel extreme obligate alkaliphilic Bacillus marmarensis DSM 21297 is known to produce polyhydroxybutyrate (PHB). However, the detailed mechanism of PHB synthesis in B. marmarensis is still unknown. Here, we investigated which metabolic pathways and metabolic enzymes are responsible for PHB synthesis in order to understand the regulatory pathway and optimize PHB synthesis in B. marmarensis. In accordance with the fact that beta-galactosidase, 3-hydroxyacyl-CoA dehydrogenase, and Enoyl-CoA hydratase together with acyl-CoA dehydrogenase and lipase were annotated in B. marmarensis according to the RAST server, we used glucose, lactose, and olive oil to understand the preferred metabolic pathway for the PHB synthesis. It was found that B. marmarensis produces PHB from glucose, lactose, and olive oil. However, the highest PHB titer and the highest amount of PHB synthesized per dry cell mass (Y-P/X) were achieved in the presence of lactose, as compared to glucose and olive oil. Additionally, in the absence of peptone, the amount of PHB synthesized is reduced for each carbon source. Interestingly, none of the carbon sources studied yielded an efficient PHB synthesis, and supplementation of the medium with potassium ions did not enhance PHB synthesis. According to these experimental results and the presence of annotated metabolic enzymes based on the RAST server, PHB accumulation in the cells of B. marmarensis could be improved by the level of the expression of 3-hydroxybutyryl-CoA dehydrogenase (1.1.1.157), which increases the production of NADPH. Additionally, the accumulation of 3-hydroxyacyl-CoA could enhance the production of PHB in B. marmarensis in the presence of fatty acids. To our knowledge, this is the first report investigating the regulatory system involved in the control of PHB metabolism of B. marmarensis.
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    Öğe
    Synthesis of silver nanoflakes on chitosan hydrogel beads and their antimicrobial potential
    (Taylor & Francis Ltd, 2020) Demir, Didem; Ceylan, Seda; Atakav, Yagmur; Bolgen, Nimet
    The present study involves the fabrication of CH and CH-Ag hydrogel beads and the investigation of the antimicrobial properties. The beads were fabricated using a simple coacervation method. The successfully synthesized beads were characterized by UV-Vis and FTIR. The surface morphology, shape and diameter of the samples were determined by optical microscopy and SEM. The antimicrobial activities were determined against potential human pathogens including bacterial and fungal species. Our results demonstrated that beads can be utilized as potential materials for use in biomedical approaches including delivery systems and tissue engineering applications to prevent microbial contamination and to inhibit the growth of microorganisms.