Flow Calorimetry—A Useful Tool for Determination of Immobilized cis-Epoxysuccinate Hydrolase Activity from Nocardia tartaricans

Figures & data

Figure 1. The experimental set-up of calorimetric measurements (flow mode and mode with total recirculation of the reaction mixture) of activity of immobilized biocatalysts.

Figure 2. Exponential decay (three parameter single: y = y₀ + ae^−bx; y₀ = 3.22, a = 30.94, b = 0.033) of total bioconversion time of disodium cis-epoxysuccinate to disodium tartrate as a function of activity of cis-epoxysuccinate hydrolase in cells N. tartaricans immobilized in CPG beads. Conditions of bioconversion: 1 M disodium cis-epoxysuccinate (pH 7.6), 1% (w/v) sodium deoxycholate, temperature 30°C, stirring at 130 rpm, concentration of biomass 6–8.7 mg (dry weight)/1 g gel.

Table 1. Storage stability of cis-epoxysuccinate hydrolase in N. tartaricans (8.4 mg dry weight/g CPG) immobilized in hardened CPG measured by stirred or flow conditions using HPLC, isotachophoresis, respectively FC method

		Activitya (U/mg)/index of relative activityd Days
Conditions	Analytical method (U/mg)	0	7	90	355
Stirred batch reactor	HPLC	21.8	60.1/1	68.3/1	75.8/1
Stirred batch reactor	Isotachophoresis	—	52.1/0.86	67.2/0.98	—
FCb	FCb	—	51.8/0.86	67.9/0.99	77/1.02
Stirred flow reactorc	HPLC	—	58.3/0.97	—	73.2/0.97

^aThe preparation was stored in 1 M disodium cis-epoxysuccinate (pH 7.6) at 4°C; the activity is reported in Materials and Methods.

^bSingle flow mode, activity was calculated from Fig. 3.

^cFC adapted to the differential reactor system with infinite flow recirculation.

^dIndex of relative activity: activity determined with stirred batch reactor by HPLC to various analytical methods and conditions.

Figure 3. A linear correlation between activities of cis-epoxysuccinate hydrolase (in N. tartaricans), as obtained by HPLC from stirred batch reactor, and by flow calorimetry. Activity measured by HPLC was expressed in units (U) per weight (mg) of the dry entrapped biocatalyst; activity measured by FC in ΔT (mK/mg).