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Pullulan is an extracellular glucan generated by the fermentation of Aureobasidium pullulans, its safe, non-toxic, edible, low calorific value, plastic film is good, the film-forming oxygen and nitrogen permeability pole low, it is widely used in food preservation, packaging bags, additives, pharmaceuticals, pesticides, sewage treatment, and many other fields, has great development prospects and value. Expand the training process experimental study in the following aspects Aureobasidium mold shape change, physical and chemical mutagenesis, mutagenic Strain and media optimization, fermentation tanks, research results have certain value. By microscopic observation and photomicrography mastered the basic law Aureobasidium fungal cell growth and morphological changes in the different culture conditions. By 60Co γ-ray irradiation, UV and nitrous acid mutagenesis study bacteria sensitivity of these three mutagenic way, the three lethal mutagenesis way curve; stepwise mutagenesis, three each features more superior strains: the bacteria do not produce pigment 27 #, # 3 bacteria polysaccharide production in of fermentation late cells and pigment naturally cohesion settlement # -1 bacteria. 3, these three bacteria were optimized shake flask fermentation medium, using the method of orthogonal test for basic carbon and nitrogen sources, glucose and ammonium sulfate, Gradual Orthogonal Optimization converted to sucrose and soybean meal as carbon and nitrogen sources, optimizing results: 3 # fermentation polysaccharide highest yield 42.33g / L, sugar conversion rate of 52.9%. 4, 10-liter fermenter expanded trial, further in-depth understanding of the fermentation process parameters such as pH, dissolved oxygen, and carbon source consumption, cell growth, changes in the law. Of bacteria 3 # 3 # -1 bacteria # 3 bacteria within 72 hours or highest polysaccharide production 29.7g / L, sugar conversion rate of 55%. 5, bacteria # 27 and # 3 -1 bacteria showed that The 27 # bacteria can maintain long-term yeast cell morphology, culture process rarely dye secreted into the fermentation broth, but its lower polysaccharide yield; 3 # -1 bacteria polysaccharide production expansion of cultured the fermentation late cells and pigment natural cohesion settlement, the easily fermented liquid separation, following extraction of the polysaccharide is extremely favorable, fermenter just under 3 # bacteria, but its long fermentation period, extended to five days or more. Surrounded by several strains of mutant characteristics we need to do more in-depth improvement and optimization. 6, medium optimization process oxygen shock on cell growth and polysaccharide production, oxygen shock may maintain some form of cells, resulting in the increase of polysaccharide production. The oxygen shock occurred by chance, his understanding is still very superficial and do not have enough tests to illustrate its mechanism, careful observation of this phenomenon will further expand the trial process in the future.
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