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Deactivation kinetics and the effects of additives on storage stability and structure of D-psicose 3-epimerase

Zhang, Qiao, Jiang, Bo, Zhang, Tao, Duan, Zhenhua
Biotechnology letters 2018 v.40 no.1 pp. 173-179
additives, ascorbic acid, ethylene glycol, half life, models, psicose, storage quality, storage temperature
OBJECTIVE: To explore deactivation kinetics and the effects of some additives on the activity and conformational changes of D-psicose 3-epimerase (DPEase) during its storage. RESULTS: The experimental data of DPEase inactivation during storage at 4–45 °C fitted with the first-order expression model. The inactivation rate constants of DPEase stored at 4, 10, 25, 35 and 45 °C were 0.0076, 0.01, 0.0223, 0.0351 and 0.0605 day, respectively. A regression formula of half-lives as storage temperatures, ln t ₁/₂ = 4.7396/T × 10³ − 12.536, was obtained. MnSO₄ at 0.15 g l⁻¹ enhanced the residual activity by 16% after 15 days and 17% after 30 days compared with control, but 2 g ascorbic acid l⁻¹ reduced activity by 69 and 58% at the same time. In addition, 0.15 g MnSO₄ l⁻¹ and 20 g ethylene glycol l⁻¹ maintained the secondary and tertiary structure of DPEase. CONCLUSIONS: MnSO₄ and ethylene glycol actively promoted the storage and conformational stability of DPEase. In contrast, ascorbic acid was disadvantageous.