Browsing by Author "Vardar-Sukan F."

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    Aeration-enhanced bioethanol production
    (Elsevier, 2014) Deniz I.; Imamoglu E.; Vardar-Sukan F.
    coli KO11 was studied under microaerated conditions.44% higher ethanol production was achieved using aeration. In recent years, growing attention has been devoted to maximize the product yield for the conversion of biomass into ethanol. In this study, microaerated conditions were established to enhance the ethanol yield by Eschericia coli KO11. According to the results, limited aeration was found to be an important factor to increase the ethanol yield by improving the consumption of sugars and the production of biomass. The best result was obtained using oxygen transfer rate (OTR) of 5. mmol/L/h, reaching 19.66. g/L of ethanol at 48. h using quince pomace as substrate. The assays showed that less than 5% of the initial sugar remained at the end of the fermentation, achieving a biomass concentration of 7.3. g/L. In conclusion, we successfully carried out lab-scale production of bioethanol from quince pomace using the ethanologenic E. coli KO11. In particular, microaerobic ethanol fermentation at OTR = 5. mmol/L/h is suggested for the efficient utilization of sugars in quince pomace. Considering the abundance of raw material and the ease of large-scale production, this improvement will have a considerable impact on the total cost of bioethanol. © 2014 Elsevier B.V.
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    Production, purification and characterization of a proteolytic enzyme from Streptomyces sp. 2M21
    (Taylor and Francis Ltd, 2019) Deniz I.; Zihnioglu F.; Öncel S.S.; Hames E.E.; Vardar-Sukan F.
    The recent application studies on keratinase lead to new application areas for the enzyme to be used in novel industries such as pharmaceuticals and biodegradable composites. Thus, designing an economical and environmentally friendly keratinase production and purification with new features turned into an intriguing objective for its commercialization. In this study, keratinase enzyme was produced using a bioreactor of 5 L by a native Streptomyces sp. 2M21 and purified by ion exchange chromatography using step-wise gradient with 24.1-fold purification. Purified keratinase showed optimum activity at pH 9 and 30 °C. The enzyme was shown to be able to decompose different complex substrates such as chicken feather, wool and nail. Moreover, the addition of DTT enhanced the hydrolysis of wool and chicken feather to 3.4- and 3.2-fold, respectively. The potential of Streptomyces sp. to produce significant levels of keratinase using feathers as a substrate might establish cleaner applications for the production of high value-added products and degrading of keratin-containing wastes. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.
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    Effect of Agitation and Aeration on Keratinase Production in Bioreactors Using Bioprocess Engineering Aspects
    (Springer, 2021) Deniz I.; Demir T.; Oncel S.S.; Hames E.E.; Vardar-Sukan F.
    Streptomyces sp. 2M21 was evaluated for keratinase production in bioreactors using chicken feathers. Firstly, optimization of bioengineering parameters (agitation and aeration rates) using Response Surface Methodology was carried out in 2 L bioreactors. Optimized conditions identified by the modified quadratic model were verified as 150 rpm and 1 vvm experimentally corresponding to 351 U/ml of keratinase activity. Moreover, scaling up sequentially to 20 L bioreactors was implemented using constant impeller tip speed and constant mass transfer coefficient as key scale-up parameters. The keratinase activity in 5, 10 and 20 L bioreactors showed similar results with the one of shake flasks (412 U/ml) and 2 L bioreactors (351 U/ml)with respect to the keratinase activity values of 336, 385 and 344 U/ml, respectively. The results suggest keratinase production by evaluating chicken feathers in commercial level. Furthermore, this study has potential to contribute industrial scale production of keratinase by Streptomyces sp. 2M21 using the proposed bioreactor conditions. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.