Breeding Strains With High Conversion Rate Of Hydrocortisone

In the conversion of Hydrocortisone(HC)from RSA(17?-hydroxy-4-ene-3,20-dione progesterone-21-acetate)by Absidia coerulea,because of degradation of strain,results in many problems,including low conversion rate,high byproducts and so on.A screening method was established by atmospheric and room temperature plasma(ARTP)and ARTP-LiCl mutagenesis to get high conversion rate of Absidia strain in this study.On the other hand,exploring the suitable fermentation conditions and studying the performance of the mutant strain.A primary screening method of Absidia was established.The cultured strain,with the colony color cultured for 2d and colony color,back colony morphology and coarseness of mycelium for 6d was choosen as the primary screening conditions.The isolated strain of the highest conversion rate as the starting strain was mutagenized by ARTP,the time was 30s,35s and 55s,then a high-yielding strain of positive mutation A-42 was screened out according to the strain colony morphology after fermentation screening,and its conversion rate of HC could be reached 69.85%.Then choosing the strain A-42 as the starting strain,was mutagenized by ARTP-LiCl,eventually a strain(AL-172)of high HC conversion rate was obtained after primary and secondary screening.The resulted showed that after 36h of converting,the HC conversion rate could reach 74.87%,increased by 19.96%compared with the original strain and its genetic stability was good.The strain AL-172 fermentation medium was optimized through the single factor experiment.The added amount of glucose,corn steep liquor,ammonium sulfate and yeast in the medium was optimized,and the best medium formula was:glucose 8g/L,corn steep liquor 12g/L,ammonium sulfate 5g/L,yeast 2.5g/L.At this time,conversion rate of HC was the highest.Then on the basis of the medium,the shaker fermentation process was optimized,and the optimum culture conditions obtained for fermentation were:liquid volume 30 mL,inoculum size 15%,speed 200r/min.When the concentration of RSA increased to 5g/L and the amount of ethanol unchanged,the conversion rate of HC could reach 70.09%,RSA was converted completely,and AL-172 had the strong ability of converting high concentration substrate.