CS263297B1 - Process for the pH adjustment of yeast biomass with a high content of biologically active chromium complexes - Google Patents

Abstract

During the cultivation of yeast, the source of trivalent chromium is added to the culture medium in doses proportional to the increase in yeast biomass, preferably in an amount of 1,000 to 5,000 µg Cr per 1 g of newly formed yeast dry matter. Under these conditions, the chromium salt does not inhibit cultivation, a high degree of retention of chromium in the biomass is achieved and yeast biomass with a high content of intracellular chromium is obtained. It is recommended to use yeast belonging to the species permitted for the preparation of food additives.

Description

The invention relates to a process for the preparation of yeast biomass with a high content of biologically active chromium complexes.

Trivalent chromium is an essential element for living organisms that affects some important metabolic functions. In mammals, the first and most important consequence of chromium deficiency is the impairment of glucose tolerance, manifested inter alia by a decrease in insulin efficiency, glycosuria and hyperglycemia. Chromium deficiency also causes growth retardation, decreased life expectancy, increased cholesterol and triglyceride levels, and other negative symptoms.

The daily chromium requirement for adults is estimated at 200-300 µg, for children and adolescents the chromium requirement is lower, and for the elderly it is considerably higher.

However, a significant proportion of the population has a lower daily chromium intake with all the resulting risks. In the CSSR, for example, the daily intake of chromium is estimated at 50 to 100 µg.

In eliminating the consequences of chromium deficiency, especially in restoring glucose tolerance, the organic complex containing trivalent chromium, which was first detected in brewer's yeast and called glucose tolerance factor (GTF), has a much higher biological effect than simple inorganic chromium compounds. This complex contains in addition to chromium amino acids glycine, glutamic acid and cysteine and especially nicotinic acid.

The natural sources of organic chromium complexes in brewer's yeast are relatively low (about 2 µg / g) and therefore procedures for the preparation of yeast biomass with a high content of intracellular disease are being developed. In the process of U.S. Pat. No. 4,343,905, the GTF content of brewer's yeast is increased up to 2000 µg / g by reacting the yeast suspension with a solution of nicotinic acid, 1-glutamic acid, glycine, 1-cysteine and oxide chromitý. According to U.S. Pat. No. 4,348,483, a yeast product with an intracellular chromium content of up to 1,000 µg / g is prepared by treating a suspension of live yeast Saccharomyces cerevisiae at pH 4-7 under non-growth conditions with an aqueous solution of non-toxic chromium salt for about 30 minutes. The yeast thus treated is either directly concentrated, washed and dried or, after the addition of nutrients, is propagated by cultivation, in which the content of intracellular disease is stabilized and reduced to the desired value.

In these known methods of enriching microbial biomass with biologically active chromium, chromium salts are generally added to the microbial suspension at the beginning of the process in relatively large quantities. The use of a high concentration of chromium ions inhibits the reproduction of microbial cells and therefore the chromium enters the non-reproducing cells by passive transport or during very slow cultivation.

The proportion of chromium that is incorporated into the cells is relatively low and the intracellular chromium concentrations achieved are also low.

These disadvantages are overcome by a process for the preparation of yeast biomass with a high content of biologically active chromium complexes batch-fed by periodic or continuous yeast cultivation in the presence of a trivalent chromium source according to the invention, wherein chromium salts are added increments of biomass, preferably 1,000 to 5,000 µg Cr per 1 g of new yeast dry matter formed.

In a feeding periodic or continuous culture, it is preferable to dissolve the chromium salts in the carbon source used or in its aqueous solution. The dose d of chromium salt in g per 100 g of carbon source shall be calculated from the formula:

100.y.Cr d = --- where y is the assumed recovery coefficient

Cr _x is the required dose of chromium per g of yeast increment. p is the chromium content of 1 g of chromium salt.

If the obtained biomass with a high content of biologically active chromium complexes is to be used for human consumption, it is recommended to use yeasts approved for the preparation of food additives belonging, for example, to durchars of Saccharomyces cerevisiae or Torulopsis ethanolitolerans.

After completion of the culture, the yeast is separated from the mature medium, concentrated, washed with water, inactivated and optionally dried.

An advantage of the process according to the invention is that the content of chromium salts in the fermentation medium is relatively low during cultivation and does not reach toxic concentrations that would slow the growth of the yeast. Another advantage is that a high proportion, up to 80% of the added tremor, is converted to intracellular chromium and that the biomass grown contains 3,000 yug / Cr per g of dry matter. The low residual concentration of chromium salts in the mature medium facilitates yeast washing.

The process of the invention is illustrated, but not limited, by the following examples.

He did

In a laboratory fermenter with a useful content of 15 liters and achieved oxygen transfer

5.5 g of O ₂ .L ^_ ^ .h ^1, a series of five přiživovaných periodic culturing the yeast Torulopsis etanolitalerans CCY 26-58-1 Synthetic ethanol.

Before starting all cultures, 14 L of water was soaked in the fermenter, 15 g and 250 ml of a nutrient salt solution containing 35 ml of 85 wt. H 2 PO 4, 30 g

KOH, 160 g MgSO ₄ -7 H ₂ O and 0.5 g ZnSO 4 .7 Η ₂ <0. The medium was then inoculated with 300 g of yeast paste (22.5% dry matter). Cultivations were conducted at 33 ° C, pH adjusted to 4.0 with 10% ammonia solution, and ethanol concentration in the media was maintained between 0.15 and 0.25% v / v on a Netrex. Cultivations were terminated when 314 g was consumed absolute ethanol.

The differences between the individual cultures were the amount of chromium salt added. Cultivation No. 1 was control without Cr addition, for cultures 2 to 5, a graded amount of CrCl ₃ .6H ₂ O was dissolved in the fed-batch.

After the cultivation, the yeast was separated from the medium, washed with water and centrifuged into yeast paste. The paste was resuspended in drinking water for milk of 16% dry matter. The milk was inactivated by heating at 80 ° C for 30 minutes and then dried in a laboratory spray drier. The results obtained in the comparative cultures are summarized in Table 1.

Table 1

Cultivation Cr content in ethanol mg Cr / g a. a. Growth tychlost h-i Yeast yield. dried from ethanol gq ^-1 Amount product 94% dry Cr content in product mg.g ^- · ¹ · Retention Cr% 1 - 0.43 0.80 339 - - 2 0.95 0.39 0.79 335 0.73 82 3 1.91 0.34 0.71 305 1.62 82 4 3.82 0.25 0.50 238 3.40 67 5 5.73 0.19 0.47 229 4.50 ⁵⁴

From the results it is evident that in cultures 2 and 3 the growth rate and yield were not significantly reduced compared to the control and the Cr retention in biomass was 82%. The addition of Cr per 1 g of yeast dry matter increments was 1,200 and 1, respectively. 2700 / ag. In cultures 4 and 5, higher doses of Cr significantly reduced growth rate and recovery, and chromium retention in biomass was also lower.

and

Example 2

In the same fermenter as in Example 1 and under similar culture conditions, fed periodic cultivation of Saccharomyces cerevisiae RIFXS 104 on sucrose was performed. The medium was inoculated with 300 g of compressed yeast (27% dry matter), during cultivation, the sucrose solution was metered into the fermenter with a sudden drop in the carbon dioxide concentration in the exhalation. The cultivation was stopped after 270 g of sucrose had been consumed. Chromium-potassium sulfate was added to the medium together with the β-sucrose solution in an amount corresponding to 1.37 µg Cr per 1 g of sucrose. The cultivation resulted in a growth rate of 0.25 h ^-1 and a yield of 0.4 gg 1. The addition of Cr per 1 g of the newly formed yeast dry matter was 3,425 pg. 201 g of dried yeast (94% dry matter) was obtained with a content of 1530 µg Cr / g. 81% of the metered chromium was transferred to biomass.

Example 3

Batch cultivation of Saccharomyces cerevisiae RIFIS 104 on sucrose was carried out in the fermenter described in Example 1. Prior to cultivation, the fermenter was soaked

14.5 l of water, 150 ml mineral nutrient solution (Example 1), 5 g ammonium sulfate, g urea and 300 g sucrose were added. the culture medium was inoculated with 120 g of compressed yeast (27% dry matter). During cultivation, the temperature was maintained at 30 ° C and a chromium chloride solution was dosed into the fermentation medium by means of a pump. Doses of Cr increased during the cultivation in proportion to the increments of yeast biomass, verified by a prior control experiment. The end of the cultivation was indicated by a sharp increase in dissolved oxygen after consumption of the carbon source. The cultivation yielded 0.38 g of yeast dry matter from 1 g of sucrose and 230 mg of chromium salt was dosed into the medium, corresponding to a dose of 2,017 / g Cr per g of yeast dry matter produced. 150 g of dried yeast (94% dry) containing 1,240 µg Cr.g ^{-1 was} prepared. Cr retention in culture was 81%.

Example 4

In the fermenter with an effective volume of 2.5 1 and elicited oxygen transfer 5.3 g of O ₂ .L ^-1 .h ^-1 by a continuous culture of yeast Torulopsis ethanolitolerans Synthetic ethanol. The cultivation was conducted at a addition rate of 0.25 h ^-1 , a temperature of 33 ° C and a pH of 4.0.

Within 0.25 h ^-1 , 33 ° C and pH 4.0. During the cultivation, 625 ml.h ^{-1 of} fresh medium was added to the fermenter, which contained 20 g of ethanol, 15 ml of mineral nutrient solution (Example 1), 0.6 g (NH 4 I SO 2), 2.5 g urea and 0.154 g CrCl ₃ .6H ₂ O. the same volume of medium mature leaving the digester overflow equilibrium concentration of yeast dry matter when culturing was 15 gl ^-1. when cultured to obtain the yield of yeast dry matter 0.75 gg ^'1, the addition of Cr per 1 g increment biomass reached 2,000 / TG. the product with 93% solids containing 1488 /ig.g ¹ and passed into the biomass 80% of added chromium.

Claims (3)

OBJECT OF THE INVENTION Process for the preparation of yeast biomass with a high content of biologically active chromium complexes batch-fed by periodic or continuous cultivation of yeast in the presence of trivalent chromium, characterized in that chromite salts are added to the fermentation medium continuously or in periodic doses % of biomass, preferably 1,000 to 5,000 pg Cr per g of newly formed yeast dry matter. 2. A process according to claim 1, characterized in that in the periodic or continuous cultivation of the chromium salt it is dissolved in the carbon source or in its aqueous solution. ³ 3. The method of claim 1, wherein the yeast used is Saccharomyces cerevisiae or Torulopsis ethanolitolerans.