The production of glucose from lignocellulosic materials is a major hurdle in th
ID: 478197 • Letter: T
Question
The production of glucose from lignocellulosic materials is a major hurdle in the production of biofuels from renewable resources. -Glucosidase from Aspergillus niger is investigated as a potential component in an enzyme cocktail for cellulose hydrolysis at elevated temperatures. The activity of 5.1 mg/L of -glucosidase is measured at temperatures from 30°C to 70°C using cellobiose as substrate. The results are as follows.
Temperature (°C) max (mmol l1 min1)
30 456
45 1250
50 1590
60 2900
70 567
(a) Estimate the optimum temperature for cellobiose hydrolysis. (b) Evaluate the Arrhenius parameters for thermal activation of -glucosidase. (c) What is the maximum rate of cellobiose hydrolysis at 55°C?
Doran, Pauline M.. Bioprocess Engineering Principles (Kindle Locations 18229-18243). Elsevier Science. Kindle Edition.
Explanation / Answer
From the given data,
(a) optimum temperature for cellobiose hydrolysis is 60 oC
(b) Activation energy Ea
ln(k2/k1) = Ea/R[1/T1-1/T2]
ln(2900/1590) = Ea/8.314[1/323 - 1/333]
Ea = 53742.1 J
Arrhenius parameter A
k = Ae^(-Ea/RT)
2900 = Ae^(-53742.1/8.314 x 333)
A = 7.80 x 10^11 mmol-1.min-1
(c) rate k2 at 55 oC
ln(k2/1590) = 53742.1/8.314[1/323 - 1/328]
k2 = 2157.2 mmol-1.min-1
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