Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Citation - WoS: 21Citation - Scopus: 29Partial Purification and Kinetic Characterization of Mushroom Stem Polyphenoloxidase and Determination of Its Storage Stability in Different Lyophilized Forms(Elsevier Ltd., 2007) Şimşek, Şebnem; Yemenicioğlu, AhmetMonophenolase (1011 ± 626 U/g AP) and diphenolase activities (5163 ± 3059 U/g AP) of PPO in acetone powders (APs) of different mushroom stems varied considerably. However, the limited variation of average dipenolase (L-DOPA) to monophenolase (L-tyrosine) activity ratio (5.4 ± 0.7) in crude extracts showed the homogeneity of PPO from different mushroom stems. The change in extraction material or partial purification method (ammonium sulfate or acetone precipitation) did not affect the temperature stability, temperature and pH dependency and Km of monophenolase activity considerably. However, some changes were observed in pH stability and substrate specificity of PPO in different parties of mushroom stems. The most important aspects of mushroom stem PPO are its lower diphenolase to monophenolase activity ratio than mushroom cap PPO, low temperature dependency of activity between 25 and 40 °C (Ea = 30 kJ/mol), broad optimum pH between 6 and 8, but lack of activity pH ≤5, and ability to use phloridzin as substrate. The mushroom stem PPOs partially purified and lyophilized by using sucrose, dextran or alginate showed moderate to high stability at -18 °C for 6-6.5 months. Thus, the mushroom stems obtained as a waste material during mushroom processing may be used as a more homogenous source than whole mushrooms to obtain PPO used for different industrial, clinical or research purposes.Article Citation - WoS: 110Citation - Scopus: 120Alkaline Protease Production From Alkalophilic Bacillus Sp. Isolated From Natural Habitats(Elsevier Ltd., 2006) Gençkal, Hande; Tarı, CananBacillus strains isolated under extreme alkaline conditions (Izmir, Turkey), were screened and identified for high alkaline protease activity. Strains with high protease yields were optimized with respect to inoculum concentration, temperature, agitation speed, initial medium pH and incubation time. Three Bacillus strains coded as I18, L18 and L21 showed high potential, for alkaline protease activity (160-222 U/ml) among 85 isolates. The specific growth rates were estimated from the growth curves as 0.49 h-1 for I18, as 0.6 and 0.7 h-1 for L18 and L21, respectively. The optimum temperatures were determined as 30 °C for strain I18 and 37 °C for the strains L18 and L21. Similarly, the optimum agitation speeds were 100 rpm for I18 and 180 rpm for L18 and L21. For all three strains, the optimum inoculation ratio and incubation time, were determined as 5% (v/v) and 96 h, respectively. The optimum initial media pH was found as pH 10 for strain L18 and L21. Bacillus sp. L21 with the highest specific protease activity (60 U/mg protein) and a broader pH range was chosen for further study. The biomass and product yield for this strain was determined as 0.023 g cell/g glucose and 0.021 U/g glucose, respectively. The crude enzyme of this strain was further characterized and was determined as a bleach stable, serine alkaline protease with an optimum temperature of 60 °C and a pH of 11, with a potential to be a candidate for the applications in the detergent industry.