A genetically engineered arginine deiminase reconstructed by site-directed mutagenesis belongs to the technical field of genetic engineering technology. Its amino acid sequence is shown as SEQ ID No. 1. In the amino acid sequence of the arginine deiminase reconstructed by site-directed mutagenesis, glycine at position 264 is mutated to proline, compared to an amino acid sequence of native arginine deiminase. Compared with wild type enzyme, the effective pH range effect of the mutated arginine deiminase according to the present invention is broadened to a certain extent, and especially a good enzyme activity is achieved at physiological pH 7.4. With the broadening of the effective pH effect range, the mutant enzyme still has higher stability under the condition of pH 5.5-7.5. Therefore, the problem that the arginine deiminase generally is low in enzymatic activity and short in half-life in vivo under physiological conditions in clinical application for tumor therapy is solved, and a good condition for using the enzyme and an encoding gene thereof for clinical treatment is created.

A genetically engineered arginine deiminase reconstructed by site-directed mutagenesis belongs to the technical field of genetic engineering technology. Its amino acid sequence is shown as SEQ ID No. 1. In the amino acid sequence of the arginine deiminase reconstructed by site-directed mutagenesis, glycine at position 264 is mutated to proline, compared to an amino acid sequence of native arginine deiminase. Compared with wild type enzyme, the effective pH range effect of the mutated arginine deiminase according to the present invention is broadened to a certain extent, and especially a good enzyme activity is achieved at physiological pH 7.4. With the broadening of the effective pH effect range, the mutant enzyme still has higher stability under the condition of pH 5.5-7.5. Therefore, the problem that the arginine deiminase generally is low in enzymatic activity and short in half-life in vivo under physiological conditions in clinical application for tumor therapy is solved, and a good condition for using the enzyme and an encoding gene thereof for clinical treatment is created.

An arginine deiminase mutant with improved enzyme activity and temperature stability and application thereof were provided, belonging to the technical field of genetic engineering and enzyme engineering. The arginine deiminase mutant is proline, namely Gly292 Pro, mutated from glycine near an enzyme active center. A wild-type arginine deiminase arcA coding gene is molecularly modified by a site-directed mutation technique to obtain a mutant enzyme ADIG292P, which has glycine at position 292 of an amino acid sequence of the wild type arginine deiminase mutated to proline. The arginine deiminase, modified by site-directed mutation, of the present invention has 1.5 times of increase in enzyme activity and 5.43 times of increase in half-life period at 40 C. compared with the wild-type enzyme, which solves the problems of low catalytic ability and temperature stability during the catalytic synthesis of citrulline using arginine deiminase, and lays a foundation for industrial production of efficient synthesis of citrulline and medication application.

An arginine deiminase mutant with improved enzyme activity and temperature stability and application thereof were provided, belonging to the technical field of genetic engineering and enzyme engineering. The arginine deiminase mutant is proline, namely Gly292 Pro, mutated from glycine near an enzyme active center. A wild-type arginine deiminase arcA coding gene is molecularly modified by a site-directed mutation technique to obtain a mutant enzyme ADIG292P, which has glycine at position 292 of an amino acid sequence of the wild type arginine deiminase mutated to proline. The arginine deiminase, modified by site-directed mutation, of the present invention has 1.5 times of increase in enzyme activity and 5.43 times of increase in half-life period at 40 C. compared with the wild-type enzyme, which solves the problems of low catalytic ability and temperature stability during the catalytic synthesis of citrulline using arginine deiminase, and lays a foundation for industrial production of efficient synthesis of citrulline and medication application.

Disclosed is a modified microorganism producing putrescine or ornithine, and a method for producing putrescine or ornithine using the same.

Disclosed is a modified microorganism producing putrescine or ornithine, and a method for producing putrescine or ornithine using the same.

The present invention relates to the technical field of natural substance extraction. Disclosed is a method for extracting Citrulline from a watermelon. The method for extracting Citrulline from a watermelon in the present invention comprises Raw material pretreatment, ultrasound-enzymatic hydrolysis assisted solvent leaching, and purification steps. The purification step comprises microbial fermentation, ion-exchange resin purification, macroporous adsorption resin discoloration, and crystallization and recrystallization. The method for extracting Citrulline in the present invention is simple, requires a mild condition, and has a good extraction effect on Citrulline. The purity of Citrulline after purification is more than 90%. In addition, the Citrulline extracted by the method in the present invention meets the related health requirements and product quality standards, can be applied to food and health food industries as a raw material, and has natural security advantages.

The present invention relates to the technical field of natural substance extraction. Disclosed is a method for extracting Citrulline from a watermelon. The method for extracting Citrulline from a watermelon in the present invention comprises Raw material pretreatment, ultrasound-enzymatic hydrolysis assisted solvent leaching, and purification steps. The purification step comprises microbial fermentation, ion-exchange resin purification, macroporous adsorption resin discoloration, and crystallization and recrystallization. The method for extracting Citrulline in the present invention is simple, requires a mild condition, and has a good extraction effect on Citrulline. The purity of Citrulline after purification is more than 90%. In addition, the Citrulline extracted by the method in the present invention meets the related health requirements and product quality standards, can be applied to food and health food industries as a raw material, and has natural security advantages.

What is disclosed relates to the detection and identification of bacteria of the genera Salmonella and Shigella. It relates more precisely to the methods of microbiology and the culture media used for the detection, identification, isolation and/or analytical investigation of these bacteria. Relating to a method for enrichment and selective culture of bacteria of the genera Salmonella and/or Shigella contained in a biological sample. In the method, some or all of the sample is seeded in/on a culture medium including a nutrient component that favors the development and growth of the bacteria, and includes L-ornithine as a selective agent. It also covers a culture medium suitable for carrying out this method.

What is disclosed relates to the detection and identification of bacteria of the genera Salmonella and Shigella. It relates more precisely to the methods of microbiology and the culture media used for the detection, identification, isolation and/or analytical investigation of these bacteria. Relating to a method for enrichment and selective culture of bacteria of the genera Salmonella and/or Shigella contained in a biological sample. In the method, some or all of the sample is seeded in/on a culture medium including a nutrient component that favors the development and growth of the bacteria, and includes L-ornithine as a selective agent. It also covers a culture medium suitable for carrying out this method.