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    Tailor-made novel electrospun polycaprolactone/polyethyleneimine fiber membranes for laccase immobilization: An all-in-one material to biodegrade textile dyes and phenolic compounds
    (Pergamon-Elsevier Science Ltd, 2023) Kolak, Seda; Birhanli, Emre; Boran, Filiz; Bakar, Buesra; Ulu, Ahmet; Yesilada, Ozfer; Ates, Burhan
    In spite of many works on the biodegradation of textile dyes and phenolic compounds, we propose a new, inexpensive, environmentally friendly, and sustainable material based on electrospun fiber and immobilized laccase. The polycaprolactone (PCL)/polyethyleneimine (PEI) electrospun fibers were optimized and prepared by electrospinning technique according to the operational parameters like PCL concentration (12 wt%), PEI con-centration (10 wt%), voltage (16 kV), needle tip-collector distance (20 cm), and injection speed (0.7 mL/h). Next, characterization studies were performed to investigate the morphology and structure of the electrospun fibers without and with laccase. The crude laccase was obtained by cultivating the white rot fungus T. trogii (TT), and T. versicolor (TV). The resulting electrospun fibers showed a smooth surface with a mean diameter of around 560 nm, and larger diameters were observed after laccase immobilization. According to the results, immobili-zation increased the stability properties of laccase such as storage, and operational. For instance, the residual activity of the PCL/PEI/TTL and PCL/PEI/TVL after 10 repeated cycles, was 33.2 & PLUSMN; 0.2% and 26.0 +/- 0.9%, respectively. After 3 weeks of storage, they retained around 30% of their original activity. Moreover, the PCL/ PEI/TTL and PCL/PEI/TVL were found to possess high decolorization yield to remove Orange II and Malachite Green textile dyes from solutions imitating polluted waters. Among them, the PCL/PEI/TTL exhibited the highest decolorization efficiencies of Orange II and Malachite Green after 8 continuous uses at pH 5 and a temperature of 50 C, reaching over 86%, and 46%, respectively. Moreover, PCL/PEI/TTL and PCL/PEI/TVL effectively degraded the 2,6-dichlorophenol phenolic compound at an optimal pH and temperature range and exhibited maximum removal efficiency of 52.6 +/- 0.1% and 64.5 +/- 7.6%, respectively. Our approach combines the ad-vantageous properties of electrospun fiber material and immobilization strategy for the efficient use of industrial scale important enzymes such as laccase in various enzymatic applications.
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    Unveiling the effect of molecular weight of vanillic acid grafted chitosan hydrogel films on physical, antioxidant, and antimicrobial properties for application in food packaging
    (Elsevier, 2024) Bakar, Buesra; Pekdemir, Sibel Selcuk; Birhanli, Emre; Ulu, Ahmet; Pekdemir, Mustafa Ersin; Ates, Burhan
    Till now, a wide range of chitosan (CHS)-based food packaging films have been developed. Yet, the role of molecular weight (MW), which is an important physical property of CHS, in determining the physicochemical and biochemical properties of vanillic acid (VA)-grafted CHS hydrogel films synthesized using CHS with different MWs has not been investigated until now. Three kinds of CHS including low, medium, and high MWs were grafted separately with VA through a carbodiimide mediated coupling reaction. No significant difference in water resistance properties was observed with increasing MW of CHS, in contrast to obvious decrease in light transmittance and opacity. The VA-g-CHS hydrogel films exhibited significantly improved light blocking capacity. A significant improvement in antioxidant (similar to 6-fold) and antimicrobial (similar to 1.2-fold) activity was observed after grafting with VA. In contrast, the free radical scavenging and antimicrobial activity decreased with increasing MW of CHS. Most importantly, VA-g-CHS hydrogel films could maintain the freshness of cherry tomatoes for up to 10 days at similar to 25 degrees C. However, no significant difference was observed depending on the MW value of CHS. This pioneering work is of great importance in guiding the selection of MW of CHS biomacromolecule to design hydrogel films with desired physicochemical and biochemical properties.