Castellar M R, Cánovas M, Kleber H P, Iborra J L
Department of Biochemistry and Molecular Biology B and Immunology, Faculty of Chemistry, University of Murcia, Spain.
J Appl Microbiol. 1998 Nov;85(5):883-90. doi: 10.1046/j.1365-2672.1998.00601.x.
L(-)-carnitine was produced from D(+)-carnitine by resting cells of Escherichia coli O44 K74. Oxygen did not inhibit either the carnitine transport system or the enzymes involved in the biotransformation process. Aerobic conditions led to higher product yield than anaerobic conditions. The biotransformation yield depended both on biomass and initial substrate concentrations used; the selected values for these variables were 4.30 g l-1 cells and 100 mmol l-1 D(+)-carnitine. Under these conditions the L(-)-carnitine production rate was 0.55 g l-1 h-1, the process yield was 44%, and the productivity was 0.22 g l-1 h-1 after a 30 h incubation period. Crotonobetaine production, besides L(-)-carnitine, showed that the action of more than one enzyme occurred during the biotransformation process. On the other hand, the addition of fumarate at high substrate concentrations (250 and 500 mmol l-1) led to a higher metabolic activity, which meant an increment of L(-)-carnitine production.
L(-)-肉碱由大肠杆菌O44 K74的静止细胞从D(+)-肉碱转化生成。氧气既不抑制肉碱转运系统，也不抑制生物转化过程中涉及的酶。有氧条件下的产物产量高于厌氧条件。生物转化产量取决于所使用的生物量和初始底物浓度；这些变量的选定值分别为4.30 g l-1细胞和100 mmol l-1 D(+)-肉碱。在这些条件下，L(-)-肉碱的生产速率为0.55 g l-1 h-1，经过30小时的孵育期后，过程产率为44%，生产率为0.22 g l-1 h-1。除了L(-)-肉碱外，巴豆甜菜碱的产生表明生物转化过程中有不止一种酶起作用。另一方面，在高底物浓度（250和500 mmol l-1）下添加富马酸盐会导致更高的代谢活性，这意味着L(-)-肉碱产量的增加。
