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Citric Acid, is wadely used in Food,Medical and Chemical industry. Now, most of Industrial production of citric acid is used strchy materials as raw materrial, especially like use corn and corn starch as main raw material,But with the corn and other raw materials prices rise, we should suit one’s measures to choose local conditions select the appropriate raw materials.in this research,we use Early Long-Grain Nonglutinous Broken Rice as raw materials to product by by Aspergillus niger fermentation, chould reduce the cost of citric acid production and raise comprehensive utilizing rate. The main research contents:filter sort the citric acid producing strains for Broken Rice, study on the best pretreatment process, the optimum culture medium formula and the optimal fermentation conditions. Specific conclusions are as follows:(1) Use Early Long-Grain Nonglutinous Broken Rice as raw materials,Use the Co827、 r-144-131and G2B2which is the fermentation industry used widly. that three kinds of Aspergillus niger, through fermentation contrast test, the experiment result shows:The Aspergillus niger Co827acid yield the highest, reaching11.4%. Then is the G2B2, acid production reached10.5%, r-144-131relative acidity the lowest, only9.5%. So the selection of Co827, two strains were screened for TD-0168. The final selection of acid producing high and short period of Co827as an experimental strain.(2) Use Co827as original strain,through the comparison of high temperature cooking process and extrusion puffing method for pretreatment of raw materials, using shake flask contrast test, determine it is Acid amount production, The content of initial reducing sugar and so on, the experiment result shows:Use the high temperature steaming pretreatment method, initial reducing sugar is6.5g/100ml, final acid production is10.87%.Use the extrusion puffing method, initial reducing sugar is7.2g/100ml, final acid production is8.5%, Select the most appropriate method is high temperature cooking process as pretreatment of raw materials.(3) Use the high temperature steaming pretreatment method, the same experimental conditions, the liquefaction temperature and a-amylase liquefaction conditions and additives on the test liquid velocity were investigated. The experiment result shows liquefaction temperature is95℃, addition amount of liquefied enzyme30u/g. (4) Uset the culture medium of Aspergillus niger Co827and the high temperature steaming pretreatment method, the other conditions is same, though use shake flask contrast test, determine it is final Acid amount production, Select the most appropriate method for fermentation medium. the experiment result shows:The optimum concentration of carbon is18%; the best choice of nitrogen sources are inorganic nitrogen physiological acidic ammonium chloride, concentration is1%; the optimum concentration of acid promoter is0.3%, the best effect, in this optimum medium, final Acid amount production is12.4%, the sugar-conversion-rate is84%.(5)Based on establishing the optimal medium formula, some control conditions of some common laboratory of fermentation caused by fluctuations, use shake flask contrast test, determine it is final Acid amount production, Select the most appropriate method for fermentation controlling condition, the experiment result shows:The initial pH in5.5; fermentation temperature at34℃, because the table has some fluctuation, can be controlled in a certain range; the range between220r/min, acid production is stable.
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