Selection Of High Yield Riboflavin Producing Strain By Protoplast Fusion

Riboflavin (vitamin B2) is the component of oxidative-reductive coenzyme FMN and FAD in the cell and commonly in the natural food. The riboflavin produced by the microorganism fermentation is used extensively in medicine, food and reached in the feed addition agent.A strain 10 of riboflavin producing yeast of the species Candida sp. had been mutated by ultraviolet and screened in turn by the medium containing over iron concentration, depleted medium, glucose analogs and purine analogs. ㏕he strain F52 was selected by the iron sensitivity process with strain 10 as the starting population. Its riboflavin yields could be improved by 114% than strain 10. (2) The strain 0-100-1 was selected by the depleted medium with strain F52 as the starting population. Its riboflavin yields could be improved by 106% than strain F52. ㏕he strain G-1000-R was selected by the medium containing inhibitory concentration of 2-dGlucose with strain 0-100-1 as the starting population. Its riboflavin yields could be improved by 36% than strain 0-100-1. ㏕he strains TL-2 and TL-6 was selected by the medium containing inhibitory concentration of tubercidin with strain G-1000-R as the starting population. Their riboflavin yields could be improved by 12%, 14% than strain G-1000-R. ㏕he highest riboflavin production strain TL-2 have been obtained by going down to the future generation. Its yields could be improved by 4.2 times than the strain 10.The results of riboflavin's solid-state fermentation of the strain TL-2 indicate that higher riboflavin yields such as 12937.5 u g/g can be achieved with a solid medium A added 10% (wheat) barns, 28 癈, well ventilating, suitable moisture content and fermenting about 10 days.The two parental strains, YI131 and TL-2, pretreated for 20 minutes by 0.2% ?-mercaptoethanol, hydrolyzed by Lyticase. The rate of protoplast formation of strain YI131 was 98.4% while the rate of regeneration 3.90%. The rate of protoplast formation of strain TL-2 was 97.2% while the rate of regeneration 1.89%. The protoplast of strain TL-2 losing live-ability was fused with the protoplast of strainYI131 (His") by PEG. The fusants was obtained on the regenerative medium without His. The riboflavin production of the fusant YT-3 could be improved by 25% than the strain TL-2.The riboflavin measurement in <> by spectrometer can beimproved. The new measurement is suitable to the riboflavin in fermentation and morefast than the old. (1)Change the carrying out in light-hide into carrying out in thebackground of 400-1001. (2)Change the dissolving riboflavin by acid into by hot water.The results indicated that relative standard deviation of the new method could beaccepted.