Enzymatic Preparation of <span style="font-variant: small-caps">l</span>-Malate in a Reaction System with Product Separation and Enzyme Recycling

oleh: Guosi Li, Fucheng Zhu, Fangli Gu, Xinjian Yin, Qilin Xu, Menghua Ma, Li Zhu, Baowei Lu, Naidong Chen

Format: Article
Diterbitkan: MDPI AG 2022-05-01

Deskripsi

Reaction coupling separation systems using calcium fumarate as a substrate can break the reaction equilibrium and promote the production of <span style="font-variant: small-caps;">l</span>-malate. However, the low reusability and stability of fumarase limit its further application. In this study, partially purified fumarase of <i>Thermus thermophilus</i> (87.0 U mg<sup>−1</sup>) was immobilized within konjac-κ-carrageenan beads. An amalgamation of konjac and carrageenan gum (2%) was used to form the beads, and polyethylene polyamine (0.2%) and glutaraldehyde (0.1%) were used as the cross-linking agents. The pH and temperature profiles of free and immobilized fumarases were remarkably similar. The diffusion limit of immobilized fumarase caused a decline in the maximal velocity (<i>V</i><sub>max</sub>), whereas the kinetic constant (<i>K</i><sub>m</sub>) value increased. Optimization of the parameters for biotransformation by immobilized fumarase showed that 88.3% conversion of 200 mM calcium fumarate could be achieved at 55 °C within 8 h. The beads were stored for 30 days at 4 °C with minimal loss in activity and were reusable for up to 20 cycles with 78.1% relative activity. By recycling the reaction supernatant, a total amount of 3.98 M calcium fumarate was obtained with a conversion of 99.5%, which is the highest value ever reported.