DD295190B5 - Process for microbial gluconase production - Google Patents

Description

The invention relates to a process for the microbial production of gluconic acid by oxidation of glucose by means of Acetobacter methanolicus IMET11402 (DSM 8167).

The technical production of gluconic acid by oxidation of glucose is carried out with the help of molds, eg. B.

Aspergillus niger, or bacteria, preferably with species of the genus Acetobacter / Gluconobacter. In general, these are two-stage processes. The "catalyst" (biomass) can be produced according to the batch principle, but also in the continuous process according to the chemostat principle, as described e.g. in the method according to DD 236 754 A1 and DD 238 067 A1 happens. For product formation, batch operation or fed-batch operation on an industrial scale is preferred, although proposals for continuous processes are also known (DD 253 836 A1). Most methods do not work according to the chemostat principle; Rather, the substrate is offered in portions, with the process usually started at a high concentration and periodically followed by glucose in the course of the process, so that considerable substrate gradients occur (see DE-AS 1817 907). To do so has the disadvantage that the theoretically possible yield and the organism-specific productivity can not be achieved.

The object of the invention is to increase the yield and the productivity of processes for the bacterial production of gluconic acid by oxidation of glucose.

The object of the invention is to fully exploit the organism-specific performance in terms of efficiency, speed and product concentration.

According to the invention, the object is achieved in that the process is started with a glucose concentration in the range of 15 to 50 g / l and it is ensured that the glucose concentration in this region remains constant during the oxidation process. The substrate may be added in solid or liquid form. The subsequent addition of glucose is stopped depending on the desired final concentration of gluconic acid. In the interest of residual concentrations of glucose less than 2 g / l this has to be done as long as the cell damage is not yet significant. The current glucose concentration in the fens gate is monitored metrologically. In question come off-line and on-line principles, based on colorimetric and / or enzymatic methods.

example 1

The "catalyst" Acetobacter methanolicus IMET11402 (deposited with the German Collection of Microorganisms and Cell Cultures under DSM 8167) is cultivated continuously in a non-sterile 12-liter stirred fermentor under the following conditions:

Residence time: 7 h

PO ₂ 10-30%

Temperature: 32 ° C

pH value: 4.0-4.2

Carbon source: methanol, C-labeled

The required biomass suspension is added to the 12 l stirred fermentor used for the production of gluconic acid. At 31 initial charge, the biomass concentration is 3 g / L.

The actual gluconic acid formation process is preceded by a growth phase or induction phase of the acidophilic methylotrophic gluconic acid producer. For this purpose ammonium sulfate, nutrient and trace salts for a biomass increase of 3 g BTS / I are presented in the production fermentor. At the same time, 5 g / l of glucose are added. During the growth or induction phase, the following conditions are met:

Temperature 32 "C

pH 4.0

PO ₂ 10-30%

Glucose is added discontinuously after consumption. This growth or induction phase is completed after 5 hours. The biomass concentration reaches a value of 6 g / l, and the nitrogen concentration at the end of this phase is almost 0 mg / l. With the glucose addition of 10 g / l, the gluconic acid formation process is initiated, at the same time the glucose dosage is started according to the glucose consumption rate to keep the glucose concentration almost constant. After reaching a glucose acid concentration of 215 g / l is continued until a glucose degradation less than g / l. The average productivity is 16 g / l h. A yield of 0.92 g of gluconic acid per g of glucose is achieved.

Example 2

The cultivation of Acetobacter methanolicus and the induction phase are carried out analogously to Example 1. Following the induction phase, the glucose concentration is raised to 25 g / l and thus initiated the glucose acid formation process. Again, the glucose dosing is started simultaneously with the glucose dosage rate to maintain the glucose concentration at 25 g / L. Thereafter, the glucose concentration is reduced to less than 2 g / l. The glucose dosage takes place up to a Giuconsäure concentration of 205 g / l. The average productivity is 25 g / l h, the gluconic acid yield 1.04 g / g.

Comparative example

Biomass cultivation and induction phase are carried out analogously to Example 1. The glucose concentration in the fermentor is raised to 80 g / l to initiate the gluconic acid concentration. The glucose concentration of 80 g / l is kept almost constant by glucose dosage up to a giuconic acid concentration of 150 g / l. Thereafter, the glucose dosage is stopped and the glucose concentration is reduced again to less than 2 g / l. The average productivity is 26 g / l h, the yield 0.935 g of gluconic acid per g of glucose.

Claims (2)

claims: 1. A method for microbial GJuconsäuregewinnung using the bacterial strain Acetobacter methanolicus IMET 11402 (DSM 8167), characterized in that - the biomass is produced with methanol as carbon source under carbon limitation, - Then further increased under discontinuous glucose addition until the growth at the end of this phase by N-limitation is almost zero and after - The product formation process is carried out under glucose, starting with a glucose concentration between 15 and 50 g / l and this concentration is kept constant over the duration of the process by continuous addition of glucose. 2. The method according to claim 1, characterized in that the glucose concentration is 20 to 25 g / l.