Novel technological process for producing high optical purity L-lactic acid by semi-continuous high-density fermentation of Rhizopus oryzae

Abstract

The invention discloses a novel technique for producing high optical purity L-lactic acid through rhizopus oryzae high cell density fermentation by a semi-continuous way, which relates to the following steps: (1) preparing rhizopus oryzae spore suspension; (2) preparing seed culture; (3) high-density thalli amplification; (4) 500L fermentation cylinder for the first batch fermentation; (5) 500L fermentation cylinder for high-density fermentation by the semi-continuous way-the first 5 times thalli proliferation and repeat fermentation; and (6) the last 20 times 500L fermentation cylinder for high-density and high-intensity repeat fermentation. The technique realizes semi-continuous fermentation by repeatedly using rhizopus oryzae thallis and increases the use ratio of raw material; the thallis are constructed in high density so that the fermentation period is shortened to be 18h and the fermentation intensity is increased to be 5.0g / (h*L), thus the technique has good industrial production prospect; the optical purity of the fermentation product of L-lactic acid is over 99.5 percent so as to satisfy the demands of foods and medicaments; and the existing demand for high-purity L-lactic acid is relieved to a great extent after industrial production.

Description

technical field [0001] The invention belongs to the field of microorganisms and fermentation engineering, and in particular relates to a process for producing L-lactic acid with high optical purity by semi-continuous fermentation of Rhizopus oryzae. Background technique [0002] Lactic acid is a common hydroxycarboxylic acid with simple structure, which widely exists in human body, animals, plants and microorganisms. Lactic acid is divided into D-type and L-type according to conformation. The human body can only metabolize L-lactic acid. Therefore, the World Health Organization advocates the use of L-lactic acid in the food and pharmaceutical industries to replace the currently widely used DL-lactic acid. L-lactic acid, L-lactate and their derivatives are widely used in food, medicine, feed, chemical and other fields. Especially in recent years, biodegradable plastics, green packaging materials and agricultural films produced by lactic acid polymerization can effectively so...

AI Technical Summary

Problems solved by technology

But at present, the production of L-lactic acid generally adopts batch fermentation process. On the one hand, Rhizopus oryzae cells are in a free or immobilized state. Only utilize 60~72 hours; On the other hand, the bacterium concentration is not high in the fermentation tank, is generally 5g / L~7g / L; Make batch fermentation time prolong thus, fermentation intensity is very low, at 2.5g / (h· L) below; Simultaneously because the mycelium of rhizopus oryzae is well-developed, it is easy to wind up on the stirring shaft in the tank, so that the stirring resistance is increased, and even agglomerates are formed to embed calcium carbonate and carbon source, so that the conversion rate of raw materials cannot be improved, Generally around 75%

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