Breeding Of Cyclodextrin Glucanotransferase High-yield Strain By Ion Implantation

Cyclodextrin glucanotransferase(CGTase) and β -cyclodextrin( β -CD) have important value in application.The CGTase used in industry is synthesized by bacteria , and can convert starch or related substrates into β -CD. There are more than twenty years in our country to begin the production of CGTase and β -CD.The CGTase activity of various strains used in factory are about 2000⁴000 IU/mL when cultivated for 30⁴0h. The cost of CGTase production is half of that of β -CD. The lower CGTase activity level of strain leads to higher cost of CGTase and β -CD production. The application of the two products are restricted by their relatively h(?)gh price.The CGTase -producing strain was mutagenized by ion implantation technology to breed high-yield strain , and the fermentation conditions of the high-yield strain were studied,so as to reduce the cost of CGTase and β-CD production.The high-yield strain B.sp. HA-1 , which CGTase activity level was 1.62-fold of that of the original strain was abtained after ion implantation. The B.sp. HA-1 strain was identified as a new strain by china general microorganism conserve center. It was found that mutagenizing effect was very good under implantation dose from 1×10¹⁴ ions/cm² to 1× 10¹⁶ ions/cm² and under implantation energy 30keV when implantation ion was N ⁺.After optimization of fermentation conditions, two optimal growth medium and the best culture condition were obtained. One optimal growth medium was comprised of 2%dextrin, 5%corn steep liquor, 0.2%,k₂HPO₄ and 0.02% (NH₄)₂SO₄. another optimal growth medium was comprised of 2%corn meal, 5%corn steep liquor, 0.2%k₂HPO₄ and 0.02%MgSO₄. The best culture condition was that the bacterium was cultivated in the growth medium when the initial pH value ranged from 8 to 9 at 28 ℃. It had also been found that it reached the peak of enzyme activity much earlier when B.sp. HA-1 strain was fermented with higher amount of inoculation. Under the...