(1) Production of broken rice syrup
Wash the broken rice, the by-product of indica rice, pick out the impurities in the broken rice, soak it in 40°C water for 2 hours, refine it with a refiner, the fineness is 40 mesh, and add water to adjust the concentration to 20°Bé. get broken rice milk;
Add liquid high temperature resistant α-amylase to the broken rice milk, and add 160 mL of high temperature resistant α-amylase per ton of broken rice. Use a high-temperature jet liquefier for liquefaction, the first injection temperature is 105 °C, and the pressure is maintained for 15 minutes. The temperature of the second injection was 130°C, and the pressure was maintained for 2 minutes. After cooling to 100℃, pump it into the laminar flow tank, add the same high temperature resistant α-amylase reaction again, add 240mL of high temperature resistant α-amylase per ton of broken rice, the reaction time is 90min, the reaction temperature is 100℃, when the solid content is The reaction end point is reached at 20%, and the broken rice liquefaction solution is obtained;
After the broken rice liquefaction liquid is cooled, the pH value is adjusted to pH 4 with dilute hydrochloric acid, saccharification enzyme is added, 1000g of saccharification enzyme is added per ton of broken rice, the saccharification time is 60h, and the saccharification temperature is 60°C to prepare the broken rice saccharification liquid;
Use a filter press to filter the broken rice saccharification solution, the temperature of the filter press is 60°C, and the pressure is 0.25MPa. The broken rice sugar solution is prepared, and the broken rice sugar solution is pumped into two storage tanks respectively, one storage tank is used as a secondary seed medium substrate, and the other storage tank is used as a fermentation medium substrate for standby use.
(2) Preparation of erythritol fermentation broth
Select Moniliella acetoabutans ATCC 18455 as the starting strain;
After sterilization of the shake flask medium, a strain of Moniliella acetoabutans ATCC 18455 was added, and the culture was shaken at 30°C for 24h. The shake flask medium formula is: glucose 200g/L, corn steep liquor dry powder 3g/L, and urea 5g/L. The first-class seeds were obtained after the microscopic examination of the bacteria and the OD value and other indicators reached the standard;
Add 10g/L of potassium dihydrogen phosphate and 5g/L of magnesium sulfate to the broken rice sugar solution in one of the storage tanks, sterilize it at 120°C for 15min, pump it into the secondary seed tank, cool it to 30°C and then insert the primary seeds. 5% of the inoculum. The sterile air was filtered and sterilized and passed into the fermentation tank. The tank pressure was 0.5MPa, the ventilation volume was 0.5vvm, and the culture conditions were the tank temperature of 30°C, the rotation speed of 200r/min, and the culture time of 24h. After the microscopic examination of the bacteria and the OD value and other indicators meet the standards, the secondary seed liquid is obtained;
Add 10g/L of potassium dihydrogen phosphate, 5g/L of magnesium sulfate, 5g/L of manganese sulfate, and 0.05% of soaked rice to the broken rice sugar solution in another storage tank, then sterilize it at 120°C for 15min and pump it into the fermenter. After 30 ℃, the secondary seed solution was inserted, and the inoculation amount was 10%. The fermentation conditions were the tank temperature of 28°C. The sterile air was filtered and sterilized and passed into the fermentation tank. The tank pressure was 0.05MPa, the ventilation rate was 1vvm, the rotation speed was 400r/min, and the fermentation time was 100h. When the glucose concentration dropped to 0.5%, the fermentation end point was reached, and the erythritol-containing fermentation broth was obtained, wherein the erythritol content was 135 g/L, and the erythritol conversion rate was 43.3%.
(3) Refinement of erythritol products
After pumping the fermented liquid into the storage tank, use a plate and frame filter press for coarse filtration to remove bacteria, proteins and other substances in the fermented liquid, so as to reduce the ultrafiltration pressure. filtrate;
The crude filtrate is subjected to an ultrafiltration operation, and the membrane molecular weight cut off is 1000D to remove the remaining macromolecular substances such as bacteria, proteins, nucleic acids, and colloidal particles in the fermentation broth. The operating temperature is normal temperature, and the ultrafiltration pressure is 0.2MPa. ;
The ultrafiltrate was further nanofiltered, and the membrane molecular weight cut off was 200D to remove pigments, nucleotides, amino acids, short peptides, some salt ions, etc. in the fermentation broth. The operating temperature was 40°C, the nanofiltration pressure was 2MPa, and the concentration ratio was 15. times, to obtain nanofiltrate; the obtained nanofiltrate is concentrated to 20% of the original volume liquid by a multi-effect falling film evaporator, and then sent to the crystallization tank, and the crystallization tank retains 10% of the seeds. The total crystallization time is 60h, including 12h for growing the crystal and 48h for cooling and crystallization. The product is obtained after conventional centrifugal separation, dry packaging, and the obtained erythritol crystal is a white crystalline powder with a sucrose sweetness, no peculiar smell, a moisture content of 0.05%, and a purity of 99% erythritol.
