(1) The raw materials are all corn flour, which is directly fermented to extract citric acid, changing the traditional concept that "due to the high protein content and too rich nutrients of corn flour, the existing citric acid production strains cannot use this high-nutrient medium to metabolize and accumulate citric acid, and cannot use corn flour as raw material to ferment and directly extract citric acid." At the same time, it can reduce production costs, improve the production rate of acid, and shorten the fermentation cycle.
(2) Scanned by electron microscope, it can be seen that the corn flour particles are closely arranged and have a deep cave-like structure. The effect of liquefaction could not be achieved by the conventional liquefaction process, so the mixture of corn flour and water is heated in the liquefaction tank according to the weight ratio of 1∶4 to 1∶5. When the temperature reaches 65 °C, add 6 to 12 units of high-temperature amylase per gram of corn flour, and add 4 to 8 units of high-temperature amylase per gram of corn flour when the temperature reaches 90 °C. Keep it to complete liquefaction at 95°C; use rapid filtration to separate corn residue containing excess protein and non-fermentable solids from the liquefied liquid, and put the liquefied liquid into the fermenter; most of the filtered liquefied liquid is 7-8DP short-chain dextrin, which basically does not contain protein and other nutrients, so some protein and nutrients must be added, so that the growth bacteria of citric acid can grow and reproduce normally, and metabolize and accumulate citric acid, and then the corn residue added to the fermentation tank is added in an amount of 5 to 25% of the total weight of corn residue.
(3) Of course, other equivalent nutrients that meet the above requirements can also be added; heating and disinfection: when the temperature reaches 85 ℃, stop heating and start to cool down rapidly, and when it drops to 37 ℃, connect the seed tank to the fermenter; the citric acid-containing liquid is extracted by the calcium salt method, or sodium carbonate is added when calcium citrate is produced in the process of using the calcium salt method, and the citric acid is extracted by the metathesis method. The corn flour raw material used in the above method can also be replaced with potato flour.
(1) Use wheat flour to produce citric acid, and extract gluten with the greater economic value from wheat flour is the by-product. When wheat flour produces citric acid, due to the high protein content (accounting for 9.9% of the edible part), but the protein content should be 0.5 to 0.6% for fermentation and culture of the citric acid, so wheat flour must remove a large amount of protein, and adjust the protein content to 0.5 to 0.6%.
(2) In the method for producing citric acid by using wheat flour, in addition to citric acid, the prepared product can also include gluten with higher economic value, so that the production cost of citric acid can be reduced. At the same time, due to the high egg content in wheat flour, when using wheat flour to produce citric acid, it is not necessary to add a large amount of bran to increase egg components as when using potatoes to produce citric acid, and the cost is reduced. So using wheat flour to produce citric acid is a desirable way.