DE2118361B2 - PROCESS FOR THE PRODUCTION OF LEMONIC ACID BY SUBMERSE FERMENTATION - Google Patents

Description

The invention relates to a process for the production of citric acid by submerged fermentation from Carbohydrate-containing material with the help of the Aspergillus niger mold in the presence of metals.

It is known that trace amounts of various metals such as iron, copper, zinc have an important effect on the physiology of the organism used in the fermentation process. The metals don't just do that Growth of the organism, but they also have an effect on the carbohydrate-containing substances used Material obtained yield of citric acid. It is known that although iron is responsible for the growth of Microorganisms including Aspergillus niger is needed, but the presence of this metal is one can exert a very damaging influence on the obtained citric acid yield if this metal is in the Fermentation medium in larger quantities than in traces. Various attempts have been made to remove excess To remove quantities of this metal, for example by ion exchange, precipitation or complex processes and this also applies to the use of carbohydrate-containing materials which contain relatively small amounts of this Metal included. It was also found that, for. B. copper or morpholines can be used can to counteract the effects of excess amounts of iron.

The object of the invention is to avoid these disadvantages and to provide a method in which a Control of trace metal content is achieved in an economical and convenient manner.

This is achieved according to the invention in a method of the type mentioned in that the Fermentation of the at least partially purified carbohydrates, for example purified by ion exchange Sugar, containing solution, in the presence of stainless steel, which in addition to iron, copper and manganese additionally contains the components chromium, nickel, molybdenum and niobium and / or titanium.

The stainless steel acts as a source of trace elements, creating an optimal concentration of trace melals in the fermentation mash and thus a high yield of citric acid is achieved.

This effect is surprising since it corresponds to the conventional practice, the use of stainless steel in the production of citric acid to avoid ίο or at least contact between the fermentation solution and the stainless steel to a minimum by keeping the fermentation vats z. B. coated with rubber or by using fermentation tanks made from non-ferrous materials such as titanium, aluminum or Glass.

For the method according to the invention, stainless steels are particularly suitable, those under the designation Substance no. 1.4505 or material no. 1.4586 are known.

It is advantageous if, after adding the nutrient solution, the pH is adjusted to around 2.8. Thereafter, the nutrient solution is expediently sterilized at temperatures of 100 ^° C. or above. After it has cooled down, the stainless steel is added, unless parts of the construction of the remote fermenter, pipes or cooling coils or the entire fermenter are made of this steel.

Then, the solution is inoculated with the spores of Aspergillus niger and carried out the fermentation at about 30-32 ⁰ C. The improvement in the yield in submerged fermentation in the presence of the stainless steel compared to fermentation without the addition of metal is initially shown by Example 1, which was not carried out under optimal conditions.

_s5 B eis ρ ie 1 1

A decationized sugar solution of 20% w / v was adjusted to a pH of 2.8 after addition of sewing salts.
80 ml each of the above-mentioned solution were placed in 4 shake flasks, sterilized for ^{half an hour at 100 °} C. in the flowing steam and cooled ^{to 30 ° C.} A piece of sterilized stainless steel material no. 1.4505 (test c), and 1.4586 (test d) with a surface area ratio of 1.2 ^cm2 / 100 ml contained in the sugar solution is introduced. The other two shake flasks (experiments a and b) were left without added metal.

All 4 flasks were inoculated with a spore suspension of Aspergillus niger and about 12 at 30-32 ° C Shaken for days. The results of the fermentation are shown in the table below.

Table I.

attempt

Addition of
stainless steel

Fermentation time in
Days

Citric acid yield in%

12th 35.5 12th 30.1 11th 61.1 13th 59.8

For comparison purposes, tests were carried out with 2 different (not according to the invention) copper-free Steels made:

a) 11 liters of one partially by ion exchange purified sugar solution with a content of 25% w / v. After adding nutrient salt, sugars were

be adjusted to a pH Weri of 2.8, sterilized by flowing steam at 100 ^u C, cooled to 30 "C and transferred under sterile conditions to a glass fermenter of 150 mm diameter and 1000 mm height. The aeration was carried out by a manifold at the bottom of the fermenter. the fermenter contained a piece of stainless steel material no. 1.4541 with a surface area of 131 cm- '. the fermentation broth was inoculated niger at 30 ⁰ C with Aspergillus. After 14 days Gärzeil 614 g citric acid were crystalline. obtained, corresponding to a yield of 22.3%.

b) The fermentation solution treated as in a) was placed in a fermenter as described in a), which had a piece of stainless steel according to Sioff no. 1.4571 with a surface area of 131 cm- '. The fermentation broth was inoculated niger at 30 ⁰ C with spores of Aspergillus and at the same time with 11 mg of potassium hexacyanoferrate-II was added. On the 3rd day 6.6 mg, on the 5th day 4.4 mg and on the 8th day 3.3 mg potassium hexacyanoferral-II were added. After a fermentation time of 12 days, 1.254 g of citric acid crystallized. obtained, corresponding to a yield of 45.6%.

Example 2

The fermentation solution treated as in experiments a) and b) of example I was placed in a fermenter as described in experiment a) which contained a piece of stainless steel according to material no. 1.4505 with a surface area of 131 cm ² . Then inoculation with spores of Aspergillus niger took place. Fermentation was then ended after 10 days. 2.456 g of citric acid were crystallized. obtained, corresponding to a yield of 89.3%.

Substance no. 1.4505 or 1.4506, which had a total surface of 0.6 cm, hung. Nine days after the Inoculation, the citric acid yield, based on the sucrose used, was determined in each case. the The results are summarized in Table II.

Table II

Composition of
to nutrient medium

Sucrose *), g / l
KH2PO4, g / l
MgSO * 7 H2O, g / l
NH4NO3, g / l
HCI to pH

Stainless steel additive *)
Substance no. 1.4505
Substance no. 1.4506

try b) c) d) a) 140 140 140 140 1.0 1.0 1.0 1.0 2.0 0.25 0.25 2.0 2.5 2.5 2.5 2.5 3.8 3.8 3.8 3.8

20 Aspergillus niger strain
ATCC 12 845
ATCC 11414

Yield in% of citric acid from 5 parallel tests each

93.6 92.9 91.2 92.2

Example 3

^r

The fermentation solution treated as in the previous examples was placed in a fermenter as described in experiment a), which was equipped with a piece of stainless steel material no. 1.4586 was provided with a surface area of 131 cm ² . After inoculation with Aspergillus niger spores, 11 mg potassium ferrocyanide was added to the fermentation mash on the 1st day, 3.3 mg on the 5th day and 2.2 mg on the 7th day. After a fermentation time of 10 days, Table III, 2.480 g of citric acid crystallized. obtained, corresponding to a yield of 90.18%.

In the experiments according to Examples 1 to 3, the Aspergillus niger strain »Van Thiegem citric acid strain ATCC 1015 «is used.

Konsumaicker EEC, category Il 0.3 cm ^2/100 ml solution

Example 5

To prove that the addition of potassium ferrocyanide in Example 3 is not for the good result is responsible, as indicated in experiments a) -d) of Example 4, proceeded and under The fermentation was carried out using the Aspergillus niger strain ATCC 12845. The fermentation medium was im Experiment a) according to Table III at the time of inoculation of potassium ferrocyanide in an amount corresponding to 0.7 ppm and on the basis of microscopic observation of the myccl growth after 24 hours more 0.5 ppm and after 72 hours of fermentation time a further 0.3 ppm was added. In comparative experiment b) of Table III no potassium ferrocyanide was used.

Example 4

The nutrient solutions given in Table II were inoculated with the Aspergillus niger strains ATCC 12845 and ATCC 11414. The nutrient medium was in each case in 500 ml Erlenmeyer flasks (fitted with a cotton wadding cap), which ^{were shaken on an orbital shaker at a temperature of 25 °} C. (eccentricity 3 cm, 280 rpm). A piece of sheet steel made of stainless steel was placed in each of the flasks

Composition of the fermentation medium attempt b) a) 140 Sucrose, g / l 140 1.0 KH2PO4, g / l 1.0 0.25 MgSO4 · 7 H2O, g / l 0.25 2.5 NH4NO3, g / l 2.5 3.8 HCl to pH 3.8 Stainless steel additive Substance no. 1.4505 + Substance no. 1.4586

55

b0 Aspergillus niger strain
ATCC 12 845

Yield in% of citric acid
from 5 parallel experiments each

90.8

+ 92.7

IV
Definition of the steels used in the examples:

Mn

Mon

Cu

other

<0.07% <0.07%

0.07%

1.0%

2% 17.5% 2.25% 20.0% 2% Nb> 8xC 2% 18.0% 2.75% 22.0% 2% Nb> 8xC 2% 18.0% - 10.0% Ti> 5xC 2% 17.5% 2.25% 11.5% Ti> 5xC 2.0% 17.5% 2.25% 20.0% 2.0% Ti 0.5%

Claims (4)

Patent claims: 1. Process for the production of citric acid by submerged fermentation of, at least partially containing purified carbohydrates, for example sugar purified by ion exchange Solutions with the help of the mold Aspergillus niger in the presence of trace elements, d a through characterized that the fermentation in the presence of stainless steel, which in addition to iron, copper and manganese additionally the components Chromium, nickel, molybdenum and niobium and / or titanium is carried out as a trace element donor. 2. The method according to claim 1, characterized in that a steel with the material no. 1.4505 or 1.4586 is used. 3. The method according to claim 1 or 2, characterized in that the contact of the stainless steel with the solution by constructing parts or the entire submerged fermenter, lines or Cooling coils made of this metal or by introducing a piece of steel into the nutrient solution is guaranteed. 4. The method according to any one of claims 1 to 3, characterized in that the stainless steel is used in a surface ^{ratio of], 2cm 2} / 100ml solution.