Breeding Of Guanosine-Producing Strain And Studies On Its Fermentation Conditions

According to the theory of metabolic control fermentation, the dissertationfocuses on the breeding and fermentation condition of guanosine-producing strain.The main research contents and results are as follows:(1)The method of chromatography paper was defined to determinateguanosine content quantitatively in the fermentation broth.The applicationconditions of this method was studied.(2)Bacillus subtilis TA1001 was used as the starting strain.By the treat ofDES,,the objective mutant TA208 ,which was adenine auxotrophy,the fastness ofmethionine sulfoxide(MSO)and 8-azaguanine (8-AG),was selected directionally.The mutant could produce guanosine15.82 g/L under the fermentation conditionwithout being optimized.(3)The seed culture conditions of strain TA208 in shake flasks were studiedin this dissertation. The proportions of seed medium were optimized by Partialleast–square (PLS) and orthogonal design method experiment. The seed cultureconditions were also studied. Under the optimum condition, strain TA208 couldproduce guanosine 20.74g/L by shaking flask batch fermentation.(4)Based on the above optimum condition, the batch fermentation wasperformed with strain TA208 in 5-liter fermentor. The result showed that the straincould produced guanosine 25.60g/L after fermentation for 48 hours. Theguanosine batch fermentation kinetics was studied based on the experimental datafrom the batch fermentation in 5-liter fermentor. Three kinetic models wereconstructed which could reflect the regularity of growth, product formation andsubstrate consumption in the process of batch fermentation. Then, throughmarquartd arithmetic by software DPS the parameters of models were obtained.The strain TA208 obtained has been potential to apply to industrialproducing, whose genetic character was very stable. Based on the data analysis inthe 5L fermentor, the proper batch fermentation models were obtained throughsoftware DPS analyzing, which would benefit the optimizing control of guanosinefermentation in industrial producing.