Lactic acid is an organic acid obtained from agricultural and sideline products through microbial fermentation and extraction. It is a monomer raw material for biodegradable and environmentally friendly polylactic acid. It is widely used in various fields such as food, beverages, pharmaceuticals, health products, chemicals, biodegradable plastics, etc.
A method for producing lactic acid by fermentation with sugar clear liquid includes the following steps: (1) raw material preparation: adding a sugar clear liquid: corn slurry solution: yeast extract in a volume ratio of 100:0.015:0.004 to a fermentation tank, with a total sugar content of 210g/L, a DE value of 92%, and a DX value of 90%. In the corn slurry solution, dry matter is 40%, protein is 45%, and acidity is 14%; (2) Heating sterilization: The temperature in the fermentation tank is 115 ℃, the pressure is 0.07Mpa, and the heating sterilization time is 15 minutes; (3) Adjusting the pH of the feed solution: Use a saturated solution of Ca (OH) 2 to adjust the pH of the feed solution to 5.4. If the saturated solution of Ca (OH) 2 is accidentally added too much, use 80% lactic acid or 35% hydrochloric acid to adjust the pH of the feed solution; (4) Add lactic acid bacteria for fermentation: Reduce the temperature of the material obtained in step (3) to 48 ℃, add 10% of the total volume of the material in the fermentation tank, maintain the temperature in the fermentation tank at 48 ℃, and continuously introduce sterile air into the fermentation tank. The ventilation flow rate is 0.75m3/h per ton of material, maintain the pressure in the fermentation tank at 0.4Mpa, stir, and maintain the pH of the material at 6.0 by adding a saturated solution of Ca (OH) 2, Detect the glucose content in the feed liquid. When the glucose content is 0, fermentation ends. This embodiment ferments for a total of 42 hours, with an acid production rate of 4.08g/L · h, acid production of 171.36g/L, residual total sugar of 0.2%, and residual reducing sugar of 0.08%.