Method for preparing xylitol by using xylose secondary mother liquor through fermentation

Patent metadata

Field	Value
Publication number	US-2024011057-A1
Application number	US-202118023496-A
Country	US
Kind code	A1
Filing date	Nov 30, 2021
Priority date	Dec 28, 2020
Publication date	Jan 11, 2024
Grant date	—

Abstract

The present invention relates to a method of preparing xylitol by using a xylose secondary mother liquor through fermentation. In the method, fermentation treatment is performed on a mixed liquid of the xylose secondary mother liquor and a xylose concentrate, and the xylose secondary mother liquor is subsequently batch-fed instead of glucose in the fermentation process. Thus, a glucose content in the fermentation system is stabilized, and some xylose is provided at the same time. In this way, the use amount of glucose and costs are reduced, and the system xylose can be relatively stabilized, thus improving the entire conversion rate. In the present invention, adding the xylose secondary mother liquor by mixed fermentation and batch feeding and the like enables the contents of heterosaccharides such as arabinose and mannose in the fermentation system to be always within a range of metabolization by fermenting strains, facilitating subsequent purification and improving the xylitol purity.

First claim

1 . A method of preparing xylitol by using a xylose secondary mother liquor through fermentation, comprising the following steps:
at step 1, adding a base liquid to a pre-ion exchange liquid of a xylose hydrolysate, then performing decolorization using an activated carbon and filtration to obtain a xylose liquid, and then performing low-temperature vacuum concentration to obtain a xylose concentrate having a refractive index of about 60% to 65%; at step 2, activating a yeast strain by using an LB plate and an LB liquid medium and activating the strains in a seed medium to OD 600 =5 to 6 so as to obtain a seed liquid; at step 3, cultivating the seed liquid in a sterilized fermentation medium in a fermentation tank to OD 600 >20; at step 4, performing a first batch feed fermentation, comprising adding a mixed liquid obtained by mixing the xylose concentrate and the xylose secondary mother liquor to the fermentation tank to, such that a xylose concentration in the fermentation tank is maintained at 85 g/L to 90 g/L; when a glucose concentration in the fermentation tank is less than 10 g/L, batch-feeding the xylose secondary mother liquor to control the glucose concentration to 10 g/L, where a total glucose addition amount is 35% to 40% of a xylose mass; at step 5, when the xylose concentration in step 4 is <30 g/L, performing a second batch feed fermentation using the method in step 4 until a xylitol concentration in the fermentation tank has no change.

2 . The method of claim 1 , wherein step 1 comprises:
adding Ca(OH) 2 to the pre-ion exchange liquid of the xylose hydrolysate to form a mixture, stirring the mixture at a speed of 30 rpm to 50 rpm for 15 min to 30 min to control pH to 3.0 to 3.5, and adding the activated carbon to the mixture and performing decolorization by stirring at a speed of 30 rpm to 60 rpm for 60 min to 90 min at a temperature of 60° C. to 70° C.

3 . The method of claim 1 , wherein, in step 1, the low-temperature vacuum concentration is performed under a vacuum pump pressure of −0.085 MPa to −0.095 MPa, at a water bath temperature of 60° C. to 70° C., at a rotation speed of 50 rpm to 60 rpm, and at a condensate flow rate of 150 mL/min to 200 mL/min.

4 . The method of claim 1 , wherein in step 2, the yeast strain is recombinant Escherichia coli IS5-M.

5 . The method of claim 1 , wherein in step 2, LB liquid medium comprises peptone 10 g/L, yeast powder 5 g/L, sodium chloride 10 g/L, and solid agar 1.5% to 2%.

6 . The method of claim 1 , wherein in step 3, the fermentation medium: comprises glucose 10 g/L, corn steep liquor dry powder 24 g/L, sodium chloride 0.5 g/L, KH 2 PO 4 3 g/L, Na 2 HPO 4 ·12H 2 O 9 g/L, and NH 4 Cl 1 g/L.

7 . The method of claim 1 , wherein in step 3, the cultivation lasts for 9.5 h to 11 h.

8 . The method of claim 1 , wherein in step 4, a mixing ratio of the xylose concentrate to the xylose secondary mother liquor is 7 to 9:1 to 3.

9 . The method of claim 1 , wherein in step 4, the first batch feed fermentation are: is performed at a temperature of 30° C., under a pH of 7, and having a dissolved oxygen of 20% to 25%.

10 . The method of claim 1 , wherein the entire fermentation time is about 75 h to 85 h.

11 . The method of claim 1 , wherein, in step 2, the seed medium comprises peptone 7.5 g/L, yeast powder 7.5 g/L, sodium chloride 10 g/L, and glucose 20 g/L.

12 . The method of claim 1 , wherein, in step 3, the cultivation is performed at a temperature of 37° C., at a stirring speed of 400 rpm, under a pH of 6.5˜7, and having a dissolved oxygen of 30% to 35%.

13 . The method of claim 1 , wherein step 4 further comprises batch-feeding 0.2 L to 0.5 L of a high concentration solution comprising 120 g to 130 g of a corn steep liquor dry powder liquid to the fermentation tank.

14 . The method of claim 2 , wherein the Ca(OH) 2 is 0.4% to 0.5% of the weight of the pre-ion exchange liquid.

15 . The method of claim 2 , wherein the activated carbon is 0.3% to 0.5% of the weight of the mixture.

Assignees

• Zhejiang Huakang Pharmaceutical Co Ltd
• Univ Zhejiang Technology

Inventors

• Zeng Xuhao
• Luo Jiaxing
• Wang Jing
• Hu Changhui
• Fang Shuncheng
• Liu Zhiqian
• Cai Xue
• Zhang Xiaojian
• Zheng Yuguo
• Li Mian

Classifications

• C12P7/18 Primary

  polyhydric · CPC title

• C12N1/205

  Bacterial isolates · CPC title

• C12N2500/34

  Sugars · CPC title

• C12N2500/74

  from fungi, e.g. yeasts · CPC title

• C12N2500/32

  Amino acids · CPC title