Method for fermenting and preparing citric acid by adding saccharifying enzyme

Abstract

The invention discloses a method for fermenting and preparing citric acid by adding saccharifying enzyme and belongs to the technical field of fermentation engineering. In the traditional citric acid fermentation, a method of mixing water and starch raw materials for size mixing and adding amylase so as to liquefy, heat, sterilize and ferment the raw materials is adopted, and in the fermentation process, saccharifying enzyme secreted by a production strain aspergillus niger per se is saccharified and fermented simultaneously. The method has the disadvantages that: a time process is needed for the aspergillus niger to grow and secrete saccharifying enzyme; and the acidity is continuously increased along with the increase of the produced acid, and the saccharifying enzyme of the aspergillus niger per se is gradually inhibited and cannot play a role in saccharifying normally at the later stage of the fermentation, so that the residual sugar content in the fermented liquor of the citric acid is higher in the end. The citric acid is prepared by the following steps of: adding the amylase to liquefy the starch raw materials, and heating for sterilization; adding a proper amount of saccharifying enzyme, and fermenting, filtering, decoloring, exchanging ions, separating, crystallizing and performing other processes according to the conventional technology. The method for fermenting and preparing the citric acid has the advantages of reducing raw material consumption, improving the conversion rate of the raw materials, improving the acid-producing rate, shortening the fermentation time and reducing CODCr discharge of wastewater.

Description

technical field [0001] A method for preparing citric acid by adding glucoamylase and fermenting after liquefaction and before inoculation. The invention relates to the technical field of fermentation engineering. Background technique [0002] Citric acid is a commonly used organic acid for food ingredients, and it is widely used in food industry, chemical industry, pharmaceutical industry, textile, leather, photography and other fields. Its production is mainly based on deep-layer fermentation of Aspergillus niger in large tanks, and corn, wheat, rice, cassava, starch or their mixtures are used as raw materials. After heating, adding amylase to liquefy the raw materials, inoculate and ferment, and then go through processes such as filtration, decolorization, ion exchange, separation, refining, and crystallization to obtain finished products. At present, the fermentation time for citric acid production is 60-70 hours, and the residual sugar concentration in the fermentation...

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Problems solved by technology

[0003] However, in the current citric acid fermentation process, during the fermentation process, the saccharification enzyme secreted by the production strain Aspergillus niger is used to carry out saccharification and side fermentation, and it takes a long time for Aspergillus niger to grow to secrete saccharification enzyme, and with the increase of acid production , the acidity continues to rise, and the glucoamylase of Aspergillus niger will gradually be inhibited, and the normal saccharification cannot be performed in the later stage of fermentation, resulting in high residual sugar in the final citric acid fermentation mash