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Production and Purification of a Thermostable Cyclodextrin Glycosyltransferase with a High Starch Hydrolytic Activity from Bacillus Licheniformis SK13.002 and Its Application for β-Cyclodextrin Production

Author: Rebaone Letsididi
Tutor: JiangBo
School: Jiangnan University
Course: Of Food Science
Keywords: Cyclodextrin glycosyltransferase Bacillus licheniformis Cyclodextrin Hydrolysis Cyclization Thermal stability
CLC: TQ28
Type: Master's thesis
Year: 2010
Downloads: 48
Quote: 0
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Abstract


Cyclodextrin glycosyltransferase enzyme (CGTases; EC 2.4.1.19) is the important enzyme in the food industry, the use of starch as a substrate production of α-1, 4 glycosidic linkage cyclic oligosaccharide - cyclodextrin ; with new properties can also be used to produce oligosaccharides. The use of alkali-tolerant strain the Bacillus licheniformis SK13.002, using different carbon sources, nitrogen sources and metal ions producing heat-stable β-CGTases. The different carbon sources, when the use of soluble starch, corn starch, maltodextrin and dextrin, it can be obtained the highest CGTase enzyme activity; CGTase yield several no significant difference. Of glucose and maltose on the production of the CGTase has metabolite repression. Organic nitrogen soybean peptone and yeast extract CGTase production is extremely beneficial; inorganic nitrogen sources are not suitable for CGTase production. Metal ions, MgS04 and FeCl2 most beneficial CGTase production. FeCl2 Fermentation has not been reported; see research reported only the FeCl2 enzyme stability. Add the iron ions in the fermentation medium CGTase synthesis promoted; ZnSO4, ZnCl2 and CuSO4 CGTase production inhibition. CGTase produced by B. licheniformis SK 13.002 significant hydrolysis of starch to produce a linear sugar Also, cyclodextrin (CD) is generated. The hydrolytic activity of CGTase is cyclized activity 4-fold. CGTase vice strengthening of the reaction of the hydrolysis reaction in the bread baking industry may be advantageous to use, but for the production of cyclodextrin will be adversely affected; because hydrolysis of sugar produced in the coupling reaction to accelerate the degradation of the cyclodextrin ring. , and thus will limit the final yield. B. licheniformis SK 13.002 producing CGTase have hydrolyzing activity can be regarded as a part of the reservation of the original enzyme function due to the long evolutionary process. This CGTase is in the intermediate stage of evolution, between the \CGTase at pH 7.0 and 6.0, respectively, with a maximum cyclization and hydrolytic activity. The cyclization and hydrolysis of the optimum temperature for 65 ° C. CGTase in the two reactions show the high-temperature activity, indicating its potential applications require high-temperature processing aspects. CGTase in the the 65 ℃ next 30 min still retains 75% of the cyclization activity; 65 ° C for 1 h, can retain 65% of the activity of cyclized; at 70 ℃, CGTase was lost (cyclization) vitality. , Has been obtained in the case of not been such as different concentrations of Ca2, substrate and other reagents optimized high CGTase thermal stability. B. licheniformis SK 13.002 CGTase This thermal stability such that it has the potential in the CD in industrialized production, after the cooking step, CGTases function before, the degree of cooling of the starch solution can be reduced - which will reduce the production costs: also No need to be pretreated with heat-resistant α-amylase on starch. This thermal stability characteristics of the enzyme protein engineering the an excellent genetic characteristics templates can rely on this template to create the issued desired properties, yet highly stable enzyme. B. licheniformis SK 13.002β-CGTase to 5% hydrolyzed starch as the substrate produced by the CD is mainly p-CD, γ-CD, supplemented by non-α-CD; product. Conversion of starch production the CD conversion rate up to 50%, with a crude enzyme solution in the case does not add any substance biotransformation conditions optimization. 24 h enzyme reaction, β-CD in the CD products accounted for 83% and 17% gamma-CD. The enzyme product of β-and γ-CDs were 20.9 g / 1 and 4.2 g / l. In the production of the CD, the conversion rate of the economy and generates no toxic complexing agent is economically very important. The characteristics of the thermal stability of the enzyme, and the product CD (β-and γ-CDs) can cause people's interest, because the CD solubility differences can be economically simply isolated and purified CD product. Therefore, this enzyme in the industrial production of β-CD on the great potential. B. licheniformis SK 13.002 produced the CGTase purified to electrophoretic purity by anion exchange chromatography and gel filtration chromatography. The results showed that the enzyme consists of two isozymes, molecular weight of 67.6 kDa and 47.3 kDa, respectively. Through a multi-step purification, the specific activity of the enzyme from the crude enzyme solution, 0.49 U / mg increased the two enzymes 9.46U/mg and 8.83 U / mg, and a purification factor of 37.3 yield was 19.1%. B. licheniformis SK 13.002 CGTase isozymes of strain is also can produce.

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