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Rational Breeding Of Aspergillus Oryzae Producing High Production Xylanase,the Optimization Of Fermentation And The Characteristics Of Xylanase

Posted on:2009-05-05Degree:MasterType:Thesis
Country:ChinaCandidate:L ShiFull Text:PDF
GTID:2120360245985172Subject:Microbiology
Abstract/Summary:PDF Full Text Request
Through the study of the effect of glucose on original strain FS018 producing xylanase,the results showed that the formation of xylanase was repressed by glucose. Combined with glucose-resistant rational screening model,Aspergillus oryzae FST036 with high production xylanase was breeded from FS018 through UV and laser mutation. The dosage of UV was irradiated at 30cm for 110 seconds with 15w ultraviolet lamp.The dosage of laser mutation was irradiated for 30min with 800mW.Through the mutation, the activity of the mutant FST036 reached 4243.59U/mL,24 percent more than the FS018's.Through single factor test,the results showed that the best carbon was bran and corncob,the optimum nitrogen was beef extract.A Plackett-Burman design was used to select 4 important factors from 8 factors which affected xylanase fermentation.They were corncob,K2HPO4,MgSO4 and initial pH in the culture medium.The optimal levels of 4 factors were determined by uniform design.Studies showed that optimal fermentation medium components(g/L)were beef extract 5.0,NaNO3 1.0,K2HPO4 1.17,MgSO4 1.26,FeSO4 0.01,bran 28,corcon 18,initial pH 7.57.After the optimization,the activity of FST036 reached 5987.36U/mL,only -0.31%differences from the prediction by uniform design.The optimization of fermentation conditions showed that the fermentation temperature was 30℃,the loading volume of medium was 45mL culture in 250mL shake flasks,the inoculation volume was 1%.After culturing duration 72h,the production of xylanase reached 6237.84 U/mL.Preliminary study of the metabolic characters of xylanase batch fermentation with FST036 was carried out.The kinetic models for cell growth;xylanase production and sugar consumption were proposed basing on Logistic equation and Luedeking-piret eqution.Xylanase formation was associated with the growth of FST036.The calculated results of models were compared satisfactorily with the experimental data.The characteristics of xylanase were studied.The optimum temperature was 55℃, and enzyme was stable below 50℃.The optimum pH was determined to be at pH 7.57 and showed to be stable in the range 4~10.The effect of metal ions on the activity of xylanase showed that 1mmol/L Mg2+strongly activated the activity,but Ag+,Hg2+, Mn2+and Ba2+inhibited the activity.
Keywords/Search Tags:xylanase, Aspergillus oryzae, resistance to glucose, Fermentation optimization, Plackett-Burman design, uniform design, Fermentation kinetics, characterisitics of enzyme
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