Method for preparing L-sodium lactate with high optical purity

Abstract

The invention relates to a novel process for producing L-sodium lactate by the continuous fermentation of a thermophilic bacterial strain, which is used for producing L-lactic acid with a high optical purity. The method comprises the following steps of: based on an L-lactic acid high-yield strain RY-18 bred by a gene cloning method, producing the L-lactic acid by fermenting a starchiness or glucose raw material, wherein the optical purity of the L-lactic acid can reach over 99.5 percent; producing magnesium lactate by using MgCO3 as a neutralizer of fermentation liquor, and reacting the produced magnesium lactate and NaOH under the condition that pH is 9.5 to 10.8 to obtain L-sodium lactate and Mg(OH)2 which is processed and then used as a new neutralizer MgCO3 circularly; and preparing an L-sodium lactate product with a concentration of more than or equal to 99.5 percent from L-sodium lactate pulp by decoloration, nanofiltration, distillation and purification under a reduced pressure and concentration, wherein the optical purity of the product is more than or equal to 99.5 percent. Besides, the conversion ratio of glucose in the invention is more than or equal to 92 percent, a fermentation degree is more than or equal to 170g / L, and a fermentation period lasts for 35h. In the invention, the major production processes can be continuously operated, the neutralizer of the fermentation liquor can be recycled, and the environmentally-friendly L-sodium lactate with the high optical purity can be produced with low energy consumption.

Description

technical field [0001] The invention relates to a method for using microorganisms to synthesize L-lactic acid with high optical purity and continuously produce L-lactic acid sodium salt, belonging to the field of biotechnology. Background technique [0002] Sodium lactate is an organic acid salt obtained after the neutralization reaction of lactic acid and sodium hydroxide, and is hygroscopic. It can be freely mixed with water, ethanol or glycerin. The pure product is a colorless or light yellow transparent viscous liquid. Lactic acid sold on the market has different concentrations of 40% to 80% due to differences in production processes and uses, and there are also a small number of products with a content of more than 90%. Generally, commercially available sodium lactate is mostly racemic DL-type sodium lactate, and there is also L-sodium lactate with low optical purity. [0003] Since its development, sodium lactate has played an important role in the food, cosmetic and...

AI Technical Summary

Problems solved by technology

[0012] Despite the feasibility of magnesium lactate as a fermentation neutralizer for the production of other lactates, the use of Mg(OH) 2 As a neutralizing agent, because its degree is smaller than the lactic acid produced by fermentation, the reaction needs to be carried out under vigorous stirring, and the separation and purification steps of the new lactate generated after the reaction of the generated magnesium lactate and alkali are seldom described in detail, especially from Lactic acid fermentation broth as the initial production of continuous production of lactate Not mentioned

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