Screening Of The L-Ornithine Producing Strain

L-ornithine, which exists in many kinds of tissue and cell, plays important roles in organism metabolism. It is intermediate product of urea producing and precursors of many amino acids such as arginine and citrulline. L-ornithine takes part in the urea cycle and detoxifies the high concentration of ammonia in the body. It is mainly used in preparing the compound amino acid infusion which shows effects on liver protecting and anti-fatigue. At present, there are four methods to prepare L-ornithine: extraction, chemical, fermentation and enzymatic method. Enzymatic method is preparing ornithine by arginase which exists in animals, plants and microorganisms widely. This thesis researched the screening of ornithine carbamyl transferase deficient strain, and the process of transforming L-ornithine through immobilized microbial cells, and spectroscopic properties of the interaction between L-ornithine and bovine serum albumin, aiming at finding a low-cost, easy-operation, high-quality L-ornithine production line and laying the foundation for industrial production of L-ornithine in the future.By mutagenizing the Bacillus thuringiensis preserved in our laboratory, I confirmed that 0.9% ammonium acetate was added into culture medium as inorganic nitrogen sources and DES processing time was 5min and UV irradiation time was 1min in complex mutagenesis.The use of 5% PVA and 2.5% carrageenan as the carrier for immobilization was identified in this paper. After 9h of immobilization, the operation of immobilization was of high stability, which could be repeatedly conducted 7 times with the output of L-ornithine remaining unchanged.In addition, the optimal conditions for preparation of converting L-ornithine through immobilized cells in the shaker were identified: temperature 30℃, pH 10.0, reaction time 24h, L-arginine concentration 100g·L-1, then the highest output of L-ornithine was received 31.04g-L-', which was 71.24% of the output by method with free cells.Spectroscopic properties of the interaction between L-ornithine and bovine serum albumin were studied to find that the static quenching exited between them. In physiological conditions, their quenches constant Ksv was 296.2L·mol-1, speed constant Kq was 2.962×1010L·mol-1·s-1, binding site n was 0.96319, binding constant KA was 227.9L·mol-1. The binding ability between them was not strong and could be greatly affected by pH.