JPS5841838B2 - Glucose manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for producing glucose by bringing a starch hydrolyzate solution or a solution containing a polysaccharide of two or more saccharides into contact with immobilized glucoamylase.

Conventionally, when producing glucose industrially from starch, starch is first obtained using an acid or a liquefying enzyme to obtain a starch hydrolyzate solution, a so-called dextrin solution, and then glucoamylase, which is a saccharifying enzyme, is added to the hydrolyzate solution. Then, a glucose solution is produced by reacting for 30 to 70 hours at a temperature of 50 to 60°C and a pH of 4.0 to 5.0.

However, this method requires only one use of the enzyme and purification to remove organic and inorganic impurities caused by the addition of glucoamylase. A method has been proposed in which a glucose solution is obtained by bringing the hydrolyzate solution into contact with immobilized glucoamylase.

Further, the use of the immobilized glucoamylase is attracting attention not only when obtaining glucose from a hydrolyzate of glucose, but also when obtaining glucose from a solution containing polysaccharides of disaccharides or more.

For example, there is the treatment of raffinate generated when a mixed sugar solution of fructose and glucose is chromatographically separated.

In other words, when producing fructose industrially, currently, a mixed sugar solution of glucose and fructose is produced by treating purified fuctose with an isomerase enzyme, imerase, and then the mixed solution is treated with a strong acid in the form of calcium. The liquid is passed through a cation exchange resin for chromatographic separation, and the raffinate, or glucose solution, that flows out first is returned to the isomerization step, which is the previous step, and the extract, or fructose solution, that flows out is used as a product. However, in addition to glucose, the raffinate contains various polysaccharides such as oligosaccharides and more, and if this is returned to the isomerization process, the polysaccharides will gradually become concentrated and cause trouble.

Therefore, it is preferable to convert the polysaccharide present in the raffinate into glucose and then return it to the isomerization step.

When converting the polysaccharide in the raffinate to glucose, glucoamylase can be used in the same manner as in the saccharification of the dextrin solution described above.

However, the raffinate has been significantly purified before the chromatographic separation step or isomerization step, and therefore, adding glucoamylase to the raffinate will contaminate the purified sugar solution with organic and inorganic impurities, and it will have to be purified again. It requires a process and is unfavorable in terms of cost.

Therefore, when immobilized amylase is used in the treatment of such raffinate, the treatment solution will not be contaminated with impurities.

In this way, when immobilized glucoamylase is used instead of conventional soluble glucoamylase when converting a starch hydrolyzate solution or a solution containing polysaccharides into glucose,
It has the advantage that the step of removing organic and inorganic impurities from the treatment liquid can be omitted, and its industrial value is great.

By the way, when immobilized glucoamylase is used to convert a starch hydrolyzate solution or a solution containing polysaccharides into glucose, the enzyme reaction is usually carried out by passing the solution through a packed bed of immobilized glucoamylase. If the solution is passed through the immobilized glucoamylase packed bed for a long time, microorganisms will generate in the packed bed and inhibit the enzyme reaction, and in extreme cases, the packed bed will be clogged with microbial slime, making it impossible to pass the solution. It had drawbacks.

Generally, measures to prevent the growth of microorganisms include adding an oxidizing agent, adjusting the pH to the acidic side, or keeping the temperature at high temperatures. However, in the case of immobilized glucoamylase, under these conditions, none of these methods occur. Glucoamylase is deactivated, causing serious problems with the enzymatic reaction.

The present invention solves the drawbacks of using conventional immobilized glucoamylase, and provides a method for producing glucose that effectively prevents the generation of microorganisms and does not interfere with the enzymatic reaction of immobilized glucoamylase. The purpose is to produce glucose by contacting a starch hydrolyzate solution or a solution containing polysaccharides of two or more saccharides with immobilized glucoamylase, by adding a weak acid such as acetic acid, lactic acid, or butyric acid. The present invention relates to a method for producing glucose, which comprises bringing the solution whose pH has been adjusted to 2.5 to 3.4 into contact with immobilized glucoamylase.

The present invention will be explained in detail below.

The present inventors investigated various conditions that would not interfere with the enzymatic reaction of immobilized glucoamylase and would effectively prevent the generation of microorganisms, and found that the pH was lowered to 2 by adding weak acids such as acetic acid, lactic acid, butyric acid, etc. A starch hydrolyzate solution adjusted to .5 to 3.4 (hereinafter referred to as dextrin solution) or a solution containing polysaccharides of disaccharides or more (hereinafter referred to as polysaccharide solution)
It has been found that the above objective can be achieved only when contacting with immobilized glucoamylase.

In the present invention, when the pH is set in the range of 2.5 to 3.4, the use of a so-called strong acid such as hydrochloric acid or sulfuric acid has the advantage of not increasing the ion content of the solution.

However, adjusting the pH using such a strong acid is not preferable because the immobilized glucoamylase is rapidly deactivated.

On the other hand, as an acid for pH adjustment, a so-called weak acid such as acetic acid, lactic acid, valeric acid, butyric acid, etc. is used to adjust the pH to 2.5 to 3.4.
This prevents the immobilized glucoamylase from rapidly deactivating and can effectively prevent the generation of microorganisms.

The reason why the deactivation rate of immobilized glucoamylase differs depending on the acid used even within the same pH range is not clear at present, but the lower the PKaO value of the acid used, the more the immobilized glucoamylase The deactivation rate tends to be fast.

Therefore, it is better to use a so-called weak acid with a large PKa value. However, if an acid with a too large PKa value is used, the amount of addition must be increased to bring the pH to a predetermined value, which will reduce the ion content of the solution. This is not desirable because it increases

Therefore, it is better to use a weak acid that does not greatly increase the deactivation rate of immobilized glucoamylase and does not increase the ion content of the solution to a large extent.
Lactic acid, valeric acid, butyric acid, etc. are preferred.

These weak acids can be used alone or in combination; however, as shown in the examples, it is preferable to use a mixed acid of lactic acid and acetic acid from two points of view: increase in ions in the solution and deactivation of immobilized glucoamylase. is most preferred.

In addition, the present invention uses a weak acid as explained above to lower the pH to 2.
．． A dextrin solution or a polysaccharide solution adjusted to 5 to 3.4 is brought into contact with immobilized glucoamylase, but if the pH is lower than 2.5, the deactivation rate of immobilized glucoamylase is fast even if a weak acid is used. Furthermore, if the pH is 3.4 or higher, the effect of preventing the generation of microorganisms will be reduced, which is not preferable.

In addition, when the pH-adjusted solution is brought into contact with immobilized glucoamylase, heating in the range of 40 to 60°C is preferable to room temperature, and usually the temperature is around 50°C and the pH is adjusted to 3.
．． It is preferable to contact the immobilized glucoamylase under conditions around 0.0.

The immobilized glucoamylase used in the present invention is a so-called immobilized glucoamylase that does not elute when glucoamylase is adsorbed onto various carriers such as cellulose, wood flour, alumina oxide, or ion exchange resin, and brought into contact with a solution. Any immobilized glucoamylase can be used.

As explained above, the present invention effectively solves the problem of generation of microorganisms, which is the biggest drawback when using immobilized glucoamylase. It is possible to convert this into a saccharification process, and it is possible to achieve reductions in enzyme costs through long-term use of enzymes, labor savings through continuous saccharification, etc., and the benefits brought to the glucose manufacturing industry by the present invention are significant.

The present invention will be explained in more detail below by way of Examples.

Example 1 50 to 100 mesh giant mesh type medium basic anion exchange resin Amberlite (registered trademark, hereinafter the same) IRA-
35 (manufactured by Rohm & Co., USA, the same applies hereinafter) 1.
0? Maltose adsorbed with 670 units of glucoamylase (AMC20OL from Novo, Denmark, hereinafter the same) (international standard units, PH 4, 5, 50°C) at room temperature, and the pH was adjusted to 2.5 to 3.4 with various acids. liquid at 50℃
, SV4, the half-life of the activity of the immobilized glucoamylase and the number of viable bacteria in the exit solution on the final day were as shown in Table 1.

Example 2 680 units of glucoamylase (international standard potential, PH 4, 5, 50°C) was adsorbed to 50 to 80 meshes of diethylaminoethylated wood flour i, oy by a conventional method, and acetic acid 1
When a 25% dextrin solution with a pH of 3.3 at 0 mmol/L was passed at 50°C and 7.01111/Hr, a sugar solution with a glucose content of 80% was obtained for 10 days without the generation of microorganisms. was gotten.

Example 3 670 units of glucoamylase (international standard unit PH4
, 5,50°C), and added 10 mmol/L of acetic acid and 2 mmol/L of lactic acid, and adjusted the pH to 3.1. 78% glucose content, 17% oligosaccharide content, 5% fructose content) at 5.0'C1
When the solution was passed at a rate of 20 ml/hr, a sugar solution with a glucose content of 86% was obtained over 10 days without the generation of microorganisms.

Claims (1)

[Claims] 1. When producing glucose by contacting a starch hydrolyzate solution or a solution containing polysaccharides of two or more saccharides with immobilized glucoamylase, add a weak acid such as acetic acid, lactic acid, or butyric acid to adjust the pH to 2.5 or more. 3. A method for producing glucose, which comprises bringing the solution prepared in 4 into contact with immobilized glucoamylase.