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    AFB1 recognition from liver tissue via AFB1 imprinted magnetic nanoparticles
    (Elsevier, 2022) Erdem, Veli Ziya; Basegmez, Hatice Imge Oktay; Pesint, Gozde Baydemir
    Aflatoxins (AFs) are produced mainly by Aspergillus flavus and Aspergillus parasiticus and aflatoxin B1 (AFB1) is one of the most toxic aflatoxins with its carcinogenic property. AFB1 recognition from samples is very important and PHEMA based AFB1 imprinted magnetic nanoparticles (magAFB1-MIPs) were synthesized for the selective AFB1 recognition from liver tissue. The AFB1-MIPs were synthesized in different mole ratios and NIPs were synthesized for control. Characterization studies of magAFB1-MIPs and NIPs were carried out by swelling tests, surface area measurements, scanning electron microscopy and particle size analysis. The surface area was found as 117 m2/g and the size of the nanoparticles were found as 483 nm in diameter. The percentage yield of polymerization was calculated as 98 % and the template (AFB1) removal ratio from the magAFB1-MIPs was calculated as 91 %. The maximum adsorbtion capacities were calculated as 427.57 ng g-1 for magAFB1-MIPs and 44.6 ng g-1 for magNIPs. Selectivity tests showed that magAFB1-MIPs adsorb AFB1 1.74, 4.40, 2.46 times selective than that of AFB2, AFG1 and AFG2 molecules, respectively. AFB1 removal amount from AFB1 spiked liver tissue was satisfactory and recorded as 10.4 ng g-1 and 54.8 ng g-1 for 2 ng g-1 and 10 ng g-1 spiked liver tissue samples, respectively. AFB1 adsorption amount decrease was found negligible for 10 consecutive adsorption-desorption repeats in reusability study.
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    Effect of waste grape pomace on citric acid bioproduction by submerged fermentation
    (United Arab Emirates Univ, 2021) Basegmez, Hatice Imge Oktay
    Citric acid is of great economic importance due to its wide range of applications. Citric acid, which is a versatile and widely used organic acid, constitutes 60% of organic acids used in the food industry and 10% of those in the pharmaceutical industry. Citric acid is produced using various agricultural wastes as a substrate through solid state or submerged fermentation. In this study waste grape pomace was proposed as a valuable substrate alternative for citric acid production using submerged fermentation. Initially screening of citric acid production capacity was conducted using 6 different Aspergillus niger strains (3 wildtype strains isolated from dried figs and 3 commercial ATCC strains) on synthetic medium. The wild type AN2 was determined as the highest producing strain with 14.32 mg/mL citric acid following 192 h fermentation. Then the waste grape pomace concentration effect on citric acid production was studied by five different concentrations in the range of 100-300 g of pomace in 1 L medium for 192 h fermentation. Using the wild type AN2 strain the highest production of citric acid and yield was achieved with 250 g/L grape pomace concentration as 28.26 mg/mL and 87%, respectively. Moreover, biomass production of the strains in grape pomace medium showed similar pattern with the citric acid production except biomass formation was increased with the grape pomace concentration increases. This study presented that comparing with synthetic medium waste grape pomace can be valuable substrate alternative for citric acid production using submerged fermentation. The study also contributed to the literature as waste grape pomace could be valuable substrate for future research studies.
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    Enhanced laccase separation from fermentation medium using cryogel columns
    (Elsevier, 2023) Eren, Burcu; Zenger, Okan; Basegmez, Hatice Imge Oktay; Pesint, Gozde Baydemir
    The laccase enzyme family belongs to the oxidoreductase enzyme class and is one of the most commercially valuable enzymes that catalyzes the oxidation of one electron of a wide range of phenolic compounds. Separation and purification of laccases are crucial for industry since they play an important role in dye decolorization, biodegradation and food processing. Therefore, developing effective, high yielding and cost-effective methods for laccase production is vital. In this study, it was aimed to prepare cryogel columns for laccase purification following the bioproduction of laccase via Aspergillus niger. 2-hydroxyethyl methacrylate based cryogels were synthesized in the presence of 1-vinylimidazole as the affinity ligand and characterized by swelling tests, Bru-nauer-Emmett-Teller surface area measurement and scanning electron microscopy analysis. Surface area and water uptake ratio of cryogel columns were 35 m2/g and 93 %, respectively. The effect of pH, equilibrium laccase concentration, flow rate, interaction time and temperature on laccase adsorption were examined. The purifi-cation factor was calculated as 10.53 under optimum conditions and the enzyme recovery was found to be 86.7 % from fermentation medium. Current study revealed that laccase purification using cryogels following filtration of fermentation medium could be a promising candidate for industrial applications with eliminating the need for complex chromatographic steps.
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    Tannic acid purification from pomegranate peel via tannic acid imprinted particle-embedded cryogel column
    (Elsevier, 2023) Pesint, Gozde Baydemir; Cemek, Kardelen; Zenger, Okan; Anar, Baris Can; Basegmez, Hatice Imge Oktay
    Tannic acid (TA) is hydrolysable tannin found in the leaves and bark of many herbaceous and woody plants. Purification of TA is important due to its antibacterial, antihistaminic, antioxidant, antimutagenic and antitussive properties. In this study, 2-hydroxyethyl methacrylate-based TA-imprinted particle embedded cryogel (TA-MIP) was synthesized to purify TA from pomegranate peel. Furthermore, non-imprinted particle embedded cryogel (NIP) was synthesized to determine specific adsorption properties of TA-MIP, and control cryogel was synthesized without embedding procedure. The synthesized cryogel columns were characterized via scanning electron microscopy, Brunauer-Emmett-Teller surface area analysis, fourier-transform infrared spectroscopy, and swelling studies. Particle-embedding procedure resulted in a significantly higher specific surface area of particle-embedded columns (TA-MIP and NIP, 29 m(2)/g and 25 m(2)/g, respectively) than the specific surface area of control cryogel (9 m(2)/g). Adsorption studies were performed from aqueous solutions and maximum TA adsorption was found to be 34.4 mg/g for TA-MIP, 3.9 mg/g for NIP, and 2.8 mg/g for control cryogel. Within the scope of selectivity study, it was demonstrated that the synthesized columns have a high selectivity for TA against gallic acid (GA) and quercetin (QCT). Finally, purification of TA directly from pomegranate peel extract was studied and results were confirmed by HPLC. Furthermore, it has been proven that TA-MIP cryogel columns can be repeatedly used up to ten-times without any remarkable reduction in the TA adsorption amount.