52 results about "Sucrose isomerase" patented technology

The invention is directed to novel enzymes that convert sucrose to isomaltulose. More particularly, the present invention discloses novel sucrose isomerases, polynucleotides encoding these sucrose isomerases, methods for isolating such polynucleotides and nucleic acid constructs that express these polynucleotides. Also disclosed are cells, including transformed bacterial or plant cells, and differentiated plants comprising cells, which contain these sucrose isomerase-encoding polynucleotides, as well as extracts thereof. Methods of producing isomaltulose are also disclosed which use the polypeptides, polynucleotides, cells, cell extracts and plants of the invention.

The invention discloses an Erwiniarhapontici NX-5 and a method of producing sucrose isomerase for the preparation of isomaltulose by the Erwiniarhapontici. The strain CGMCC No.2222 is inoculated in an aseptic culture medium containing carbon source, nitrogen source, inorganic salt and water for the aerobic culture. Cells containing the sucrose isomerase are obtained after the centrifugation or the ultrafiltration. Furthermore, dissociative cells containing the sucrose isomerase are directly adopted to be converted into sucrose to generate the isomaltulose or immobilized cells containing the sucrose isomerase which are then converted into the sucrose isomerase to generate the isomaltulose. With the strain adopted, the conversion rate of the sucrose reaches to 99.5 percent (w / w), the conversion rate of the isomaltulose reaches to 90 percent, and the concentration of the isomaltulose in the conversion solution reaches to 500g / L. no hydrolysis side effects happen. Almost no glucose and fructose are contained in the conversion solution. The product, the isomaltulose, can not be converted into other components with the reaction. The invention is beneficial to the industrial production of the isomaltulose.

The present invention is directed towards genetic modification of native gene encoding for sucrose isomerase and isomaltulose synthase to substantially increase the expression level of these enzymes and use of said enzymes in a process to produce rare disaccharides such as isomaltulose and trehalulose. Also disclosed in the present invention is expression constructs comprising the modified genes and a host cells to express the same.

Sucrose isomerase is used as a nutritional supplement, or can be mixed in with a powderous food / beverage formulation. When an animal, including a human, consumes sucrose, the sucrose isomerase will act on the sucrose present in the food, and will convert the sucrose to other sugars. This results in lowering of the glycemic index of the food without changing the formulation of the food.

The invention discloses a sucrose isomerase mutant with improved stability and a construction method thereof, belonging to the fields of genetic engineering and enzyme engineering. The invention screens and obtains two mutant strains V280L and S499F with improved single-point thermostability and a combined mutant V280L / S499L on the basis of high-enzyme activity disperse Pantoea-derived sucrose isomerase. While the heat stability of the three mutants was significantly improved, the enzyme activity was not affected. These mutants in the present invention are more suitable for industrial production than natural sucrose isomerase, and have very huge application prospects and industrial value.

The invention discloses a sucrose isomerase mutant with improved thermal stability and catalytic efficiency and belongs to the technical fields of genetic engineering and enzyme engineering. According to the sucrose isomerase mutant with improved thermal stability and catalytic efficiency, site-specific mutagenes is performed on the amino acid with relatively high B factor in the sucrose isomerase crystal structure, namely mutating E at the 175 site of the sucrose isomerase into N; at the same time, E at the 175 site is further mutated into N on basis of the mutant K576D, so that two sucrose isomerase mutants with both improved thermal stabilities and catalytic efficiencies are obtained. Compared with the natural sucrose isomerase, the half life periods of the mutant E175N and the mutant E175N / K576D disclosed by the invention are respectively improved by 130% and 665% at 45 DEG C and the catalytic efficiencies Kcat / Km are respectively improved by 38% and 19%. Compared with natural enzymes, when catalysis is performed on sucrose by the sucrose isomerase mutant to produce isomaltulose, the maximum isomaltulose conversion rates of the mutants are respectively improved by 1.8% and 1.6%. Compared with natural sucrose isomerases, the two mutants obtained by the invention are more suitable for industrial applications.

The invention discloses a sucrose isomerase gene, namely a pal I gene, which has the nucleotide sequence shown as SEQ ID NO:1. The invention also discloses a coding protein for the gene, namely an SIase enzyme. The invention also discloses an expression vector and a host cell containing the gene, and a high-efficiency expression method for the gene. A recombinant strain containing the sucrose isomerase gene has isomerism activity and can transform sucrose into isomaltulose. The recombinant strain has the advantages of high stability, high catalytic efficiency, obvious improvement of product specificity, and application to industrial production of the isomaltulose.