An Innovator Support Material for Tyrosinase Immobilization: Antimony-Doped Tin Oxide Thin Films (ATO-TF)
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An Innovator Support Material for Tyrosinase Immobilization: Antimony-Doped Tin Oxide Thin Films (ATO-TF) Ayşe Türkhan 1
2
& Elif Duygu Kaya & Adem Koçyiğit
3
Received: 28 November 2019 / Accepted: 23 April 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Tyrosinase (T3824, Sigma) enzymes were immobilized onto SnO2: Sb thin films (ATOTF) which were synthesized in laboratory conditions by spray pyrolysis technique. Immobilization of tyrosinase onto SnO2: Sb thin film (ATO-TF) was confirmed by scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR). The optimum pH of the immobilized tyrosinase (tyrosinase-ATO-TF) was 6.0, and the optimum temperature was found to be 30 °C. In the presence of catechol substrate of immobilized enzymes, Km and Vmax values were determined as 0.34 mM and 312.5 U/cm2 min, respectively. The thermal stabilities of the immobilized tyrosinase at 4 °C and 30 °C were investigated for 20, 40, and 60 min. At these temperatures and time intervals, the immobilized tyrosinase was found to be highly stable. The pH stability of the immobilized tyrosinase enzymes was incubated for 24, 48, 72, and 96 h at 4 °C temperature. The enzyme activity was determined under optimum conditions, and the activity of the immobilized tyrosinase enzymes exhibited various values for the range of pH 3.0–8.0. The storage stability of the immobilized tyrosinase enzymes at 4 °C was investigated, and 45.72% of the initial activity was maintained at the end of the seventh day. Furthermore, the reusability of the immobilized tyrosinase enzymes has been examined. The immobilized tyrosinase enzymes can be used 3 times and survived their 50% of initial activity. The ATO-TF can be used as alternative support materials for the immobilization of tyrosinase enzymes. Keywords ATO-TF . Immobilization . Adsorption method . Tyrosinase
Introduction Tyrosinase (E.C. 1.14.18.1) is a copper-containing metalloenzyme which induces enzymatic browning during storage, harvesting, processing, and handling of many plant materials [1, 2]. * Ayşe Türkhan [email protected] Extended author information available on the last page of the article
Applied Biochemistry and Biotechnology
The plants, fungi, and some bacterial strains contain tyrosinase abundantly [1, 2]. Tyrosinase enzyme can be performed for two tasks: firstly, the hydroxylation reaction which converts monophenols to o-diphenols, and secondly, oxidation reaction which transforms o-diphenols to o-quinones. The obtained products at the end of oxidation reactions are converted to brown, red, or black pigments via polymerization [3]. In addition, tyrosinase enzyme has a dinuclear copper center and uses molecular oxygen in the reaction [4]. Solving the problems arising from the use of free enzymes in a positive way and the interest in enzyme immobilization to make enzymes more useful and attractive in the industry were attracted and investigated [5]. Immobilized enzymes can be easily separated from the reaction mediu
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