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Kinetics and activation energetics of death in Saccharomyces cerevisiae induced by sulfur dioxide
Author(s) -
Anacleto J.,
van Uden N.
Publication year - 1982
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260241112
Subject(s) - sulfur dioxide , activation energy , kinetics , sulfur , chemistry , entropy of activation , enthalpy , reaction rate constant , thermodynamics , inorganic chemistry , organic chemistry , physics , quantum mechanics
Death of Saccharomyces cerevisiae induced by sulfur dioxide (K 2 S 2 O 2 was used as the SO 2 source) followed saturation kinetics. The enthalpy of activation of death was not affected by concentration over the range tested (5–150) mg/L of (K 2 S 2 O 2 at pH 3.4) and averaged 3.6 × 10 4 cal/mol as compared with 8.5 × 10 4 cal/mol for Δ H ‡ of thermal death. The entropy of activation of death was hyperbolic function of the sulfur dioxide concentration, extrapolated at zero concentration to Δ S 0 ‡ = 36.8 cal mol −1 K −1 and tended to ΔΔ S max ‡ = 13.2 cal mol −1 K −1 at saturating concentration, yielding a dis0sociation constant of 5.8 × 10 −1 M sulfur dioxide. As was predicted from these results, In K d (the specific rate of death induced by sulfur dioxide) was hyperbolic function of concentration under isothermic conditions and extrapolated toa finite value at zero concentration. The Arrhenuis plots and the Δ S ± plot versus concentration revealed the occurrence of substrate inhabitation of the death effect at high concentrations (above 60 mg/L K 2 S 2 O 2 at pH 3.4). A model is presented involving two types of receptor sites for sulfur dioxide on the cell surface, on directly connected with the death process, the other modulating its entropy of activation.