Determination of kinetics and heat of hydrolysis for non-homogenous substrate by isothermal calorimetry
The competitiveness of the second-generation bioethanol by biotechnological process requires an effective and quantitative control of biochemical reactions. In this study, the potential of isothermal calorimetry technique to measure heat and kinetics of a non-homogeneous substrate enzymatic hydrolysis is intended. Using this technique, optimum temperature of the enzymes used for lignocellulosic molecules hydrolysis was determined. Thus, the amount of substrate-to-enzyme ratio was highlighted as an important parameter of the hydrolysis yield. Furthermore, a new enzymes’ cocktail efficiency consisting of a mix of cellulases and cellobiose dehydrogenase (CDH) was qualified by this technique. The results showed that this cocktail allowed the production of a high amount of gluconic acid that could improve the attractiveness of these second-generation biofuels. From the set of experiments, the hydrolysis heat of wheat straw was derived and a meaningful value of −32.2 ± 3.2 J g−1 (gram reducing sugars product) is calculated. Then, isothermal measurements were used to determine kinetic constants of the cellulases and CDH mix on wheat straw. Results showed that this enzyme cocktail has an optimal rate at 45 °C in the range of temperatures tested (40–55 °C).
KeywordsBiofuel Enzymes Hydrolysis Cellulase Cellobiose dehydrogenase
Maximum reaction rate
Substrate concentration at time t
Substrate concentration at time 0
This research was funded by the Council of the PACA Region in the frame of MOTBIO project. The authors would like to thank the Research Federation ECCOREV for partially financing this work. The authors are grateful to Simeng ZHOU from Biotechnology of Filamentous Fungi laboratory—Aix Marseille Université, INRA, UMR 1163, for biochemical analyses.
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