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    Characterization of a novel lipase bound to the Geobacillus stearothermophilus AH22 membrane
    (Springer Heidelberg, 2025) Dincer, Barbaros; Iskender, Engin; Kizil, Demet; Adiguzel, Ahmet
    Lipases (EC 3.1.1.3), used in many industrial applications, hydrolyze tri-, di-, and monoglycerides to free fatty acids and glycerol. This study aimed to determine the capacity of Geobacillus stearothermophilus AH22 for membrane-bound lipase production and to identify the optimal medium for lipase production. Following the determination of certain parameters such as pH and temperature, where the produced membrane-bound lipase exhibits the best activity, the kinetic data, as Km and Vmax, were obtained in the presence of p-NPA (0.03 +/- 0.008 mM and 0.7 +/- 0.18 U), p-NPB (0.7 +/- 0.18 mM and 3.4 +/- 0.40 U), p-NPO (0.12 +/- 0.010 mM and 5.2 +/- 0.62 U), and p-NPL (0.01 +/- 0.003 mM and 0.8 +/- 0.15 U) substrates. The highest activity of AH22 membrane-bound lipase was observed at pH 9.0 in the presence of substrates, at temperatures ranging from 20 to 40 degrees C for substrates with low carbon chains fatty acids and from 50 to 60 degrees C for substrates with long carbon chains. Also, it was observed that the cells dried by lyophilization showed lipase activity after they were pulver-ized. However, in terms of reuse, it was determined that wet cells were more efficient than powdered cells. It was found that the activity of the AH22 membrane-bound lipase had not changed much in the presence of anions and cations but decreased significantly in the presence of detergents and beta-mercaptoethanol. The AH22 membrane-bound lipase can be directly used in other industrial areas where lipase is used, except for the detergent industry, without requiring additional and expensive processing such as purification or immobilization.
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    Ecofriendly quince peel powder incorporated Polylactic acid biocomposite film
    (Sage Publications Ltd, 2024) Sen, Ibrahim; Eroglu, Murat; Severgun, Olcay; Kizil, Demet
    This study aims to develop sustainable, renewable and biodegradable biocomposite films from environmentally friendly materials. For this purpose, completely biodegradable polymer composites were prepared by mixing polylactic acid (PLA) with a new source, quince peel (QP), by solvent casting method, and their structural, mechanical and thermal properties were examined. The tensile strengths of the composites prepared using QP in proportions varying between 5% (P5Q) and 30% (P30Q) by weight vary between 21.13 +/- 0.80 and 12.01 +/- 0.10 MPa, and their elongations at break vary between 11.33 +/- 0.38 and 4.08 +/- 1.06 %. As the QP contribution increased, the tensile strength and breaking elongation of these composites generally decreased, while the elastic modulus also increased. Among these composites, whose elastic modulus varies between 1040.00 +/- 140.01 and 811.33 +/- 13.31 MPa, it was determined that the elastic modulus (1040.00 +/- 140.01 MPa) of the 20% QP added composite (P20Q) was higher than the others. When the thermal analysis of PLA/QP films were examined, it was observed that the glass transition temperatures (Tg) were between 58.54 and 51.45 degrees C and the melting temperatures (Tm) were between 167.71 and 164.28 degrees C, and these temperatures generally decreased with increasing QP doping. When the T50 values, which represent the temperature at which 50% of the composite materials decompose, were examined, it was found that the QP-added ones were higher than the pure composites. While this value was 317.96 degrees C in pure PLA composite, T50 values varied between 327.92 and 340.80 degrees C depending on the varying QP ratios. According to the XRD results performed to evaluate the crystalline properties of PLA composites containing quince bark, the crystallinity of pure PLA was determined as 19.5% and the crystallinity of composites containing 5, 10, 20 and 30 wt % QP additives was determined as 19.3, 18.3, 16.4 and 14.6%, respectively.
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    Effect of Olive Leaf Powder on Structural, Thermal, Mechanical, and Antioxidant Properties of Polylactic Acid Based Biocomposite Films
    (Wiley, 2025) Tuna, Sibel; Kizil, Demet; Sen, Ibrahim; Eroglu, Murat
    In the present study, polylactic acid films containing olive leaves with different particle sizes and different additive ratios were characterized in terms of structural, thermal, mechanical, and antioxidant properties. XRD and SEM analyses showed that PLA films with olive leaf powder generally have an amorphous structure, whereas films with low filler ratios and fine particles exhibit higher crystallinity. Not so surprisingly, neither filler amount nor mixing time are making a big difference in the crystallinity or morphology of the surface. In the context of DSC analysis, a maximum variation of 2 degrees C in the glass transition temperature was observed. A comparable trend shift was observed between the Tg (glass transition temperature for DMA) values in the DMA analysis and the Tg (glass transition temperature for DSC) values in the DSC analysis. However, the change in the DMA analysis was more definitive. Antioxidant activity of the films was observed to increase with decreasing particle size of olive leaves added to polylactic acid and increasing additive ratio. Adding olive leaf powder to PLA and then looking at the effects on these aspects as mechanical, thermal, morphological, and antioxidant properties contributed to the evaluation of PLA as a potential additive for producing biodegradable polymers.
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    Inhibition and purification of acetylcholinesterases from adults and nymphs of Ricania simulans (Walker, 1851) (Hemiptera: Ricaniidae)
    (Springer Int Publ Ag, 2022) Dincer, Barbaros; Kizil, Demet
    Ricania simulans (Walker, 1851) (Hemiptera: Ricaniidae) has been causing damage in agricultural areas along the eastern Black Sea coastline since 2006. As there are not enough studies on managing this pest, it continues to pose a threat. One of the significant control tactics of insecticides includes the inhibition of acetylcholinesterase. Therefore the present study is aimed to study an alternative way to combat R. simulans through inhibition of acetylcholinesterase (ACHE). The ACHE was purified from adults and nymphs of R. simulans one by one using one-step edrophonium-Sepharose 6B affinity chromatography, and some kinetic properties were studied. The ACHEs were purified 251.6-fold with a yield of 34.2% for adults and 65.5-fold with a yield of 2.2% for nymphs. The K-m, V-max, and k(cat) values of R. simulans ACHE for acetylthiocholine iodide (ATC) hydrolysis were determined to be 0.04 +/- 0.01 mM, 2,000.0 +/- 250 EU/mg protein and 104.5 +/- 13 min(-1) for adults and 0.02 +/- 0.01 mM, 500.0 +/- 52 EU/mg protein and 30.3 +/- 6.4 min(-1) for nymphs, respectively. In inhibition studies of R. simulans ACHEs with edrophonium chloride, tacrine and olive leaf extract with water, the IC50 values of the inhibitors were calculated. Although all inhibitors inhibited the ACHEs, they inhibited the nymphs' ACHEs more effectively. In particular, the fact that the olive leaf water extract is effective in the ACHEs inhibition of these two stages is important for it to be an environmentally friendly pesticide that can be used in the fight against this pest.
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    Investigation of Biopesticides for the Pest Control Through Inhibition of the Acetylcholinesterase Purified from Loxostege sticticalis (L.) (Lepidoptera: Crambidae)
    (Springer, 2025) Kizil, Demet
    Acetylcholinesterase (AChE) is a cholinergic enzyme called acetylcholine acetylhydrolase. Acetylcholinesterase inhibition is one of the prominent methods in studies on pest control management. In this study, AChE was purified 103.7-fold from Loxostege sticticalis (L.) using an Edrophonium-Sepharose 6B affinity column, and some kinetic properties were investigated. The molecular weight of the purified enzyme was determined by Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE). Inhibition studies of AChE were realized with tacrine, edrophonium chloride, and cypermethrin, which are known inhibitors of AChE, as well as aqueous extracts of certain plant leaves. The subunit molecular weight of purified AChE was estimated to be approximately 56 kDa by SDS-PAGE analysis. The maximum activity of Loxostege sticticalis AChE was specified at 40.0 degrees C and pH 8.0. Vmax, Km, and kcat values of the AChE were determined as 243.9 +/- 15.7 EU/mg protein, 0.122 +/- 0.06 mM, and 13.7 +/- 2.7 min-1, respectively. In the inhibition studies, the IC50 values of tacrine, edrophonium chloride and cypermethrin were found to be 3.4 +/- 0.5, 0.08 +/- 0.006 and 85.0 +/- 4.1 mu M, respectively. Besides, the IC50 values of aqueous extracts of olive leaf, alder leaf, walnut leaf, cherry laurel leaf, and plane leaf were as 12.0 +/- 0.6, 15.2 +/- 1.3, 32.1 +/- 1.5, 58.3 +/- 1.9, and 75.2 +/- 2.8 mu g dry matter/mL, respectively. In addition, the oleuropein and phenolic substance amounts of these plant extracts were determined and correlated with the IC50 values. Consequently, the plant extracts used in this study may be recommended as an alternative biopesticide source to control such pests via AChE inhibition.
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    Production Starch Using the Yeast (Cryptococcus neoformans HTM1 Strain) Isolated From Tea (Camellia sinensis)
    (Wiley-V C H Verlag Gmbh, 2025) Dincer, Barbaros; Haciosmanoglu, Emine; Kizil, Demet; Alpay Karaoglu, Sengul
    Starch is a staple food in human and animal nutrition as well as a widely used raw material in industry. This study determined the capacity of producing starch of a new yeast culture, which was defined as Cryptococcus neoformans HTM1 strain by a definitive molecular diagnosis method and isolated from tea (Camellia sinensis). The produced starch was identified as wheat starch. It was established that the HTM1 strain produced 0.23 mg/mL starch with glucose, 0.30 mg/mL with fructose, and 0.37 mg/mL with sucrose. The HTM1 strain can produce starch in media with honey and waste fruit juices; the amounts of starch were calculated as 1.2 mg/mL from honey, 1.1 mg/mL from pomegranate, 0.8 mg/mL from apple, 0.9 mg/mL from tangerine, and 0.8 mg/mL from kiwi. In conclusion, in this study, it was determined that the yeast strain C. neoformans HTM1 isolated from tea can produce starch and has the potential to produce starch in vitro regardless of environmental conditions.
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    Synthesis, characterization, colorimetric sensor and acetylcholinesterase inhibition studies of novel benzimidazole-based hydroxamic acids
    (Elsevier, 2025) Yilmaz, Fatih; Kizil, Demet; Dincer, Barbaros; Karaoglu, Kaan
    Two new hydroxamic acid molecules 2-(2-Pyridyl)benzimidazole-N-acetohydroxamic acid (HL1), 2-(2-Pyridyl) benzimidazole-N-butanohydroxamic acid (HL2), can be used in Fe(III) detection and pest control, have been synthesized first time and characterized using Elemental Analysis, 1H NMR, 13C NMR, FT-IR, LC-MS (ESI+) spectrometry. Selectivity of the HL1 and HL2 towards Fe3+ ion were tested against in the presence of the competitive metal ions and found to be highly effective agents for the determination of Fe3+ ions in the presence of these ions. The limits of detection of Fe(III) ions using these ligands were found 1.9 mu M and 0.7 mu M, respectively. Metal complexes of HL1 and HL2 with Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) were also synthesized to understand the complex formation in the solid phase and at higher pH. The results showed in the solid phase the M:L ratios of the complexes were 1:1 and 1:2 and the hydroxamate groups were in the keto form. The inhibition effects of HL1 and HL2 ligands on acetylcholinesterase (AChE) purified from Orosanga japonica (Melichar, 1898) (Homoptera: Ricaniidae) were determined. The ligands effectively inhibited acetylcholinesterase yet HL1 was more effective than HL2, IC50 values of 1.7 +/- 0.2 mM and 2.6 +/- 0.1 mM, respectively. These results indicated these newly synthesized benzimidazole-based hydroxamic acid ligands can serve as dualfunctional agents for both Fe3+ detection and pest control.
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    Ternary Transition Metal Complexes with an Azo-Imine Ligand and 2,2?-Bipyridine: Characterization, Computational Calculations, and Acetylcholinesterase Inhibition Activities
    (Slovensko Kemijsko Drustvo, 2022) Serbest, Kerim; Dural, Turan; Kizil, Demet; Emirik, Mustafa; Zengin, Ali; Dincer, Barbaros
    New mononuclear ternary transition metal complexes: [M(HL)(bipy)2]ClO4, (M: Mn(II) for 1, Ni(II) for 2), [M(HL) (bipy) (ClO4)], (M: Ni(II) for 3, Cu(II) for 4, Zn(II) for 5) with M(II), 2-[(hydroxyimino)methyl]-4-[-phenyldiazenyl] phenol, H2L, and 2,2'-bipyridine were synthesized, and their structures were investigated by using various analytical, spectroscopic techniques such as elemental analysis, FTIR, UV-Vis, NMR, MALDI-TOF mass spectrometry, thermal analysis. The theoretical studies were performed by DFT techniques by using B3LYP function with 6-311++G (d, p)/LanLD2Z basis set. The electronic transitions charters of the complexes were further analyzed by TD-DFT/CAM-B3LYP method. IR and thermal analysis data verify the proposed structures. The inhibition activities of the complexes against acetylcholinesterase (AChE) extracted from Ricania simulans adults and nymphs were examined and all the complexes were found to be active. Among the complexes studied, the highest inhibition activity was exhibited by complex 5 with the lowest IC50 value (3.2 +/- 0.8 mu M) for AChE of adults and complex 3 with the lowest IC50 value (4.6 +/- 0.8 mu M) for AChE of nymphs.