Abstract:Ornithine is a non-essential amino acid. It plays key function to discharge amino nitrogen and solve ammonia toxicity. Recently, ornithine is widely applied in the fields of the function beverage, diet, health care, liver-protecting, anticancer, and in the food and medicine industry. With the utilization of microbial resources and application of metabolic engineering in strain improvement, microbial fermentation gradually becomes the major method of ornithine production. The biosynthesis metabolic pathway and catabolic pathways of ornithine, which key enzymes are involved in,are introduced in this paper. Furthermore, the author gives a detailed description about the way of which ornithine producing strain is reformed by the metabolic engineering, involving metabolic engineering technology and the recent research progress.