Zhang Zhi-Jun, Pan Jiang, Li Chun-Xiu, Yu Hui-Lei, Zheng Gao-Wei, Ju Xin, Xu Jian-He
Laboratory of Biocatalysis and Synthetic Biotechnology, State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, China.
Bioprocess Biosyst Eng. 2014 Jul;37(7):1241-8. doi: 10.1007/s00449-013-1096-y. Epub 2013 Dec 7.
Recombinant Escherichia coli cells expressing Alcaligenes sp. nitrilase were simply immobilized by direct cross-linking using glutaraldehyde. About 85 % of the total nitrilase activity was recovered under the optimal cross-linking conditions. The thermal stabilities of the cross-linked cells measured at 30, 40 and 50 °C were 4.5-, 5.3-, and 5.1-fold those of the free cells, respectively. The concentration of (R)-(-)-mandelic acid reached 280 mM after merely 2 h transformation with the immobilized cells using 300 mM mandelonitrile as substrate, affording an extremely high productivity of 510.7 g L(-1) d(-1). In addition, operational stability of the immobilized cells was obviously superior to that of free cells, without significant activity loss after 15 cycles of batch reactions or 8 cycles of repeated fed-batch reactions. Therefore, the easy preparation and robust characteristics of the immobilized biocatalyst make it a very promising biocatalyst for high-performance and low-cost production of optically pure (R)-(-)-mandelic acid.
表达产碱杆菌腈水解酶的重组大肠杆菌细胞通过使用戊二醛直接交联进行简单固定。在最佳交联条件下，约85%的总腈水解酶活性得以保留。在30、40和50℃下测定的交联细胞的热稳定性分别是游离细胞的4.5倍、5.3倍和5.1倍。以300 mM扁桃腈为底物，用固定化细胞进行转化，仅2小时后，(R)-(-)-扁桃酸的浓度就达到了280 mM，产率极高，为510.7 g L(-1) d(-1)。此外，固定化细胞的操作稳定性明显优于游离细胞，在15个批次反应循环或8个重复补料分批反应循环后，活性没有显著损失。因此，这种固定化生物催化剂制备简单且性能稳定，使其成为用于高效、低成本生产光学纯(R)-(-)-扁桃酸的非常有前景的生物催化剂。
