Electron Beam Mutagenesis Breeding Of High ?-amylase Yield Aspergillus Niger Strain And Its Enzyme Saccharifying Power

Aspergillus Niger is a common fermentation strain which can produce?-amylase.And the activity impact on the efficiency of fermentation directly.The traditional mutagenesis methods,such as ultraviolet irradiation mutagenesis,ultrasonic mutagenesis and nitrite mutagenesis,can no longer meet the needs of industrial production.As a new irradiation technique,electron beam can greatly increase the activity of?-amylase in Aspergillus Niger and maintain a certain genetic stability.In this paper,five kinds of?-amylase producing Aspergillus Niger were isolated and cultured,thus,an Aspergillus Niger with relatively high enzyme activity was screened.The mutation breeding parameters of electron beam irradiation were optimized by the response surface method.By contrasting ultrasonic mutagenesis,ultraviolet mutation method,?-ray radiation mutation method,diethyl sulfate mutation method,nitrite mutation method and electron beam irradiation mutation method,the best method for mutagenesis of Aspergillus Niger with high yield of?-amylase was determined.By centrifugation and precipitation of fermentation broth,dialysis,anion-exchange chromatography,gel chromatography,we studied the changes of the saccharifying power of?-amylase before and after mutagenesis for Electron beam irradiation mutagenesis.By study on observation of colony morphology,spore morphology,growth curve,adsorption rate and supporting force of?-amylase and so on.The structural changes and saccharification of Aspergillus Niger were investigated to provide the basis for electron beam mutagenesis breeding of Aspergillus Niger.The results are as follows:The activity of?-amylase was measured to be 13560 U/mL.Under the optimum mutagenesis condition:Electron beam energy 6 MeV,irradiation dose 0.4 kGy,spore concentration 3×10~6/mL,the enzyme activity of the mutant strain of Aspergillus Niger was 30800 U/mL.with enzyme activity increased by 127.1%.According to the increasing extent of enzyme activity under different mutagenesis modes,the effect of the improvement in turn is as follows,Electron beam irradiation mutagenesis(127.1%)>diethyl sulfate mutagenesis(84.7%)>ultraviolet radiation mutagenesis(72.3%)>?-ray radiation mutagenesis(60.1%)>nitrite mutagenesis(36.4%)>ultrasonic mutagenesis(23.1%).Therefore,electron beam can increase the activity of?-amylase obviously,so that it can be selected as the best mutation breeding method.The morphology of the mutant strain of Aspergillus Niger was more loose than that of the morphology of spores of starting bacteria.It was beneficial to the proliferation of spores.The growth rate of the mutant strain in plate culture was significantly higher than that of the original strain.However,in the stable period,there was no significant difference in dry weight.Adsorption rate of gamma-amylase:the adsorption capacity of starting bacteria?-amylase on glutinous rice starch was 18.1%,glutinous corn starch was 3.7%.The adsorption capacity of mutant strain?-amylase on glutinous rice starch was20.1%,glutinous corn starch was 4.2%.The adsorption rate of mutant strain?-amylase on glutinous rice was increased by 2%,glutinous corn starch was increased by 0.5%.Degree of hydrolysis of?-amylase:the degree of hydrolysis of starting bacteria?-amylase on glutinous rice starch was 21.3%,glutinous corn starch was 9.6%.The degree of hydrolysis of mutant strain?-amylase on glutinous rice starch was 22.7%,glutinous corn starch was 10.2%.The degree of hydrolysis of mutant strain?-amylase on glutinous rice was increased by 1.4%,glutinous corn starch was increased by 0.6%.Hydrolytic force of gamma-amylase:the hydrolytic force of starting bacteria?-amylase on glutinous rice starch was 26.32%,glutinous corn starch was 32.19%.The hydrolytic force of mutant strain?-amylase on glutinous rice starch was35.34%,glutinous corn starch was 46.28%.The hydrolytic force of mutant strain?-amylase on glutinous rice was increased by 9%,glutinous corn starch was increased by14.1%.The mutant strain?-amylase could hydrolyze the soluble starch with high concentration,and the rate of glucose formation was 2.3 times higher than that of the original strain.