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    Characterization of thermostable ?-amylase isozymes from Lactobacillus fermentum
    (Elsevier Science Bv, 2016) Kocabay, Samet; Cetinkaya, Serap; Akkaya, Birnur; Yenidunya, Ali Fazil
    A strain of Lactobacillus fermentum producing two isozymes of a 20 kDa beta-amylase was isolated from the faecal sample of a newborn. The starin was identified by sequencing its 16S rRNA gene. The two beta-amylase isozymes were resolved and visualized by two dimensional protein gel electrophoresis (2-D gel electrophoresis). Some of the physical and biochemical properties of the enzymes were characterized. The beta-amylase displayed two optimum pH s, 5.0 and 10.0 and two optimum temperatures, 45 degrees C and 37 degrees C, respectively. The isozymes hydrolyzed different substrates: glycogen at pH 5.0, and corn starch at pH 10.0. The activity did not require Ca2+, though the activity at pH 10.0 was enhanced in the presence of 5.0 mM and 10.0 mM CaCl2, 110% and 130%, respectively. (C) 2016 Elsevier B.V. All rights reserved.
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    Production, purification, and characterization of metalloprotease from Candida kefyr 41 PSB
    (Elsevier Science Bv, 2017) Yavuz, Sevgi; Kocabay, Samet; Cetinkaya, Serap; Akkaya, Birnur; Akkaya, Recep; Yenidunya, Ali Fazil; Bakici, Mustafa Zahir
    A thermostable metalloprotease, produced from an environmental strain of Candida kefyr 41 PSB, was purified 16 fold with a 60% yield by cold ethanol precipitation and affinity chromatography (bentoniteacrylamide-cysteine microcomposite). The purified enzyme appeared as a single protein band at 43 kDa. Its optimum pH and temperature points were found to be 7.0 and 105 degrees C, respectively. K-m and V-max values of the enzyme were determined to be 3.5 mg/mL and 4.4 mu mol mL(-1) min(-1), 1.65 mg/mL and 6.1 mu mol mL(-1) min(-1), using casein and gelatine as the substrates, respectively. The activity was inhibited by using ethylenediamine tetraacetic acid (EDTA), indicating that the enzyme was a metalloprotease. Stability of the enzyme was investigated by using thermodynamic and kinetic parameters. The thermal inactivation profile of the enzyme conformed to the first order kinetics. The half life of the enzyme at 95, 105, 115, 125 and 135 degrees C was 1310, 610, 220, 150, and 86 min, respectively. (C) 2016 Elsevier B.V. All rights reserved.