Modeling cellobiose hydrolysis with integrated kinetic models |
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Authors: | Luiza P V Calsavara Flávio F De Moraes Gisella M Zanin |
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Institution: | (1) Chemical Engineering Department, State University of Maringá, Av. Colombo, 5790, BL E-46-S09, 87020-900 Maringá-PR, Brazil |
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Abstract: | The enzyme cellobiase Novozym 188, which is used for improving hydrolysis of bagasse with cellulase, was characterized in
its commercial available form and integrated kinetic models were applied to the hydrolysis of cellobiose. The specific activity
of this enzyme was determined for pH values from 3.0–7.0, and temperatures from 40–75°C, with cellobiose at 2 g/L. Thermal
stability was measured at pH 4.8 and temperatures from 40–70°C. Substrate inhibition was studied at the same pH, 50°C, and
cellobiose concentrations from 0.4–20 g/L. Product inhibition was determined at 50°C, pH 4.8, cellobiose concentrations of
2 and 20 g/L, and initial glucose concentration nearly zero or 1.8 g/L. The enzyme has shown the greatest specific activity,
17.8 U/mg, at pH 4.5 and 65°C. Thermal activation of the enzyme followed Arrhenius equation with the Energy of Activation
being equal to 11 kcal/mol for pH values 4 and 5. Thermal deactivation was adequately modeled by the exponential decay model
with Energy of Deactivation giving 81.6 kcal/mol. Kinetics parameters for substrate uncompetitive inhibition were: Km=2.42 mM, V
max=16.31 U/mg, Ks=54.2 mM. Substrate inhibition was clearly observed above 10 mM cellobiose. Product inhibition at the concentration studied has usually doubled the time necessary to reach the same conversion
at the lower temperature tested. |
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Keywords: | Cellobiase cellobiose kinetic modeling thermal stability energy of deactivation energy of activation |
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