Mutagenesis Of Aspergillus Niger Producing Glucoamylase And Optimization Of Fermentive Parameters

Glucoamylase is a single strand acidic glycoside hydrolase that possesses excision enzyme activity of starch.It is able to hydrolyze non-reducing end alpha-1,4-glycosidic linkages of starch,soluble starch and oligosaccharide to glucose.Glucoamylase is widely used in the brewing industry,sugar industry,food processing industry and antibiotics,growth hormones,amino acid fermentation industries and light industries.It plays a significant role in the production of enzyme preparation in the world.With the social improvement,material needs of human become more and more higher,and glucoamylase will be more important for national economy.Therefore,research on production techniques of glucoamylase,breeding fine strains of high-yielding,can not only improve the technical progress of traditional enzyme preparation industry,but also greatly promote the development of enzyme preparation application.Strains of industrial production(AS-cl)was used for experiment,the highest enzyme activity was 1261 U/mL by culturing with basic fermentation.Through UV mutagenesis of Aspergillus niger,a high-yield strain was obtained and named AS-UV40c.The yields of glucoamylase increased 15%than before.The genetic stability test of five generations showed that the enzyme activity of AS-UV40c had good genetic stability.To improve value of Aspergillus niger in research and industrial application,AS-UV40c was used for starting strain,the essential medium and fermentation conditions were used as basis,the optimization of fermentation medium was carried out by using single factor experiment.The best carbon source was sucrose-potatoes starch,and the best nitrogen source was sodium nitrite-soybean powder.The orthogonal experiment of carbon and nitrogen source were performed,the optimization medium formula was as below:sucrose 1.5%,potatoes starch 4.5%,sodium nitrite 0.2%,soybean powder 0.5%,potassium hydrogen phosphate 0.15%.The enzyme activity was 1739.76 U/mL by using above formulation,increased 20%comparing with the initial activity.The optimization of inoculum,initial pH and fluid volume was performed through single-factor experiment.The best conditions were 10%for inoculum,5.5 for pH and 50 mL/250 mL for fluid volume.The enzyme activity was 1812.25 U/mL under these conditions.In summary,our research results not only enhance the contents of Aspergillus niger,but also promote the industrial application of Aspergillus Niger strain by increasing enzyme production.