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286  13 Key-Study on NHase/AMase System

                    References  [20]  [20]  [20]  [18]  [18]  [28]  [28]  —  —  References  [34]  [24]  [34]  [23]  [23]




                    Inactivation constant, k d ,  or energy E ∗  a  at 4 ◦ C k d = 0.034 h −1  at 4 ◦ C k d = 0.081 h −1  at 10 ◦ Ctill k d = 0.04 h −1  S = 300 mM  E ∗ = 91.63 kJ mol −1  E ∗ = 51.57 kJ mol −1  at 30 ◦ C k d = 0.122 h −1  Inactivation constant, k d ,  or energy E ∗  a  E ∗ = 51.60 kJ mol −1  (range k d = 0.0002 h −1  5–50 ◦ C)  Negligible till 50 ◦ C  at 50 ◦ C k d









                    (kJ mol −1 )  —  38.37  —  —  —  25.54 b  37.7 c  —  77.06  —  a  —  53.40  —  a  (kJ mol −1 )  49.17  a  —  55.61  66.72  —  52.65  53.46


                    E a                           E a
           of temperature on AMase- and NHase-catalyzed reaction and on inactivation process.
                    Bioreactor configuration  Batch  CSMR  CSMR  Batch  CSMR  Batch  CSMR  Batch  CSMR  Bioreactor configuration  CSMR  Batch  CSMR  Batch  CSMR









                    ( ◦ C)                        ( ◦ C)                  One unit of nitrile hydratase, U NHase , and of amidase, U AMase , have been defined as the amount of enzyme that produces 1 μmol of product (acrylamide or acrylic acid)
                    T range  10–30  4  4  5–25  5–25  10–55  5–30  5–40  10–30  T range  5–50  10–80  5–50  10–60  10–60 per min, when the proper substrate is incubated per 20 min at 20 ◦ C, 250 rpm, 50 mM Na-phosphate buffer, and appropriate amount of cells.


                    [Enzyme] (U NHase ml −1 )  0.29  0.29  0.29  0.059  0.32  1.58  0.275  0.236  0.69–1.52  [Enzyme] (U AMase ml −1 )  0.33–1.00  0.19  0.33–1.00  0.33  0.33 a Substrate inhibited kinetics already at 200 mM even at lower concentration with Haldane equation prediction.










                Nitrile hydratase-catalyzed reaction  [Substrate] (mM)  100  100  200  500 a  200  10  10  50  50  [Substrate] (mM)  50  10  50  100  100  d k d -Valuesfor NHaseis57timeshigherthanthatfor AMaseat15 ◦ C.




           Effect                              Amidase-catalyzed reaction      b Partial control by mass transport. c Lower diffusional control.

           Table 13.2  Substrate  Acrylonitrile  Acrylonitrile  Acrylonitrile  Propionitrile  Propionitrile  Benzonitrile  Benzonitrile d  3-Cyanopyridine  3-Cyanopyridine  Substrate  Acrylamide  Benzamide  Benzamide  Nicotinamide  Nicotinamide
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