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Kinetics of the Alkaline Phosphatase Catalyzed Hydrolysis of Disodium p ‐Nitrophenyl Phosphate in Frozen Model Systems
Author(s) -
Terefe Netsanet Shiferaw,
Mokwena Kereilemang Khanah,
Van Loey Ann,
Hendrickx Marc E.
Publication year - 2002
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp020113h
Subject(s) - maltodextrin , arrhenius plot , chemistry , arrhenius equation , lactose , hydrolysis , kinetics , thermodynamics , sucrose , chromatography , organic chemistry , activation energy , physics , quantum mechanics , spray drying
The alkaline phosphatase catalyzed hydrolysis of disodium‐ p ‐nitrophenyl phosphate was studied in four model systems comprising sucrose, maltodextrin, carboxymethylcellulose (CMC), and CMC‐lactose in a temperature range of –28 to 20 °C. In the maltodextrin and CMC‐lactose model systems, the reaction rate decreased to a very low value as the glass transition temperature was approached. In the CMC and CMC‐lactose systems with low initial solute concentration, as a consequence of freeze‐concentration, a rate maximum around the initial freezing temperature was observed. The Arrhenius equation described the temperature dependence of the reaction rate both in the liquid and the glassy states in all systems studied, while a slightly curved Arrhenius plot was observed in the “rubbery” state of the CMC and CMC‐lactose systems. The WLF equation with system‐dependent coefficients described the kinetics in the rubbery state of all the model systems except sucrose, excluding the short temperature range where reaction rate enhancement with decreasing temperature was observed.