The Selection Of High Production Strain Of Levan And The Optimization Of Fermentation Conditions

Levan is mainly produce by microbes.It has high degree of polymerization,good stability and physiologically active.It can be used in food?medicine?healthcare products?cosmetic and fodder.For many questions,it can't be produced and applied inlarge-scale.In this paper,I used three different mutagenesis to screen out the mutant of high production,and then found out the optimal fermentation conditions with response surface methodology.Agrobacterium radiobacter sp.54A-42 keept by theGuangxi University is the original strain,its production is 12.0g/L.After the UV irradiation?DES and Co60 irradiation,the production of sp.A-10 screened out is 21.9g/L.The best fermentation medium was got by Factional Factorial design and Response Surface method.when sucrose7%,(NH4)2HPO4 0.15%,KH2PO40.15%,MgSO4 · 7H20 0.1%,the complex element 1.93%,corn steep liquor 0.07%,CaCO3 0.14%,the average production of mutant sp.A-10 is 23.0g/L.The ability of levan producing is closely related with the temperature?pH?inoculum concentration and time.Though the single factor experiments,the best conditions is defined:30?,pH7.0,inoculum 10%,fermentation time 75h,the best fermentation production is 23.2g/L.