JPH03224493A - Production of starch sugar having high purity - Google Patents

Abstract

PURPOSE:To obtain the subject product only by slightly increasing the treating amount in the purification process by feeding back a by-product-containing reflux of a membrane-fractionation process to the main saccharification process and feeding back a part of the reflux to a preparatory saccharification process. CONSTITUTION:A liquefied starch is preparatorily saccharified and the obtained partially saccharified liquid is filtered. The filtered partially saccharified liquid is saccharified in the main saccharification process and the obtained saccharified liquid is subjected to membrane fractionation and separated into a liquid containing high purity starch sugar and a reflux liquid composed mainly of polymeric dextrin. Subsequently, the reflux liquid is fed back to the main saccharification process and, at the same time, a part of the enzyme-containing saccharified liquid of the main saccharification process or a part of the above reduced liquid is fed back to the preparatory saccharification process.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing starch sugar, and more specifically, the present invention relates to a method for producing starch sugar. Regarding the method.

[Background Art] Starch sugars include glucose, maltose, maltooligosaccharides, and the like. Starch sugar has conventionally been industrially produced using starch as a raw material in a batch process using enzymes. The target products such as glucose, maltose, and maltooligosaccharides contained in the starch sugar obtained by the batch method account for about 40 to 95%, and also contain dextrin and the like as by-products.

However, in recent years, the demand for high purity starch sugar has increased. Therefore, methods have been proposed to purify starch sugar containing by-products. Among these, the membrane fractionation method using an ultrafiltration membrane is considered promising because of its high separation efficiency of by-products [for example, see Japanese Patent Application Laid-Open No. 52-57344].
.

In this type of membrane fractionation method, the reflux liquid containing fractionated byproducts (dextrin, etc.) is used as a byproduct, or a part of it is fed back to the saccharification process in order to increase the utilization rate of starch. It is normal for this to happen.

[Problem to be solved by the invention]

By the way, the starch liquefied liquid used as a raw material contains various impurities. Therefore, in the membrane fractionation method, in order to prevent membrane clogging due to impurities, the saccharified liquid is purified using a filtration device such as a precoat filter or a filter press after the saccharification step and before membrane fractionation. However, as mentioned above, when the fraction containing by-products (dextrin, etc.) is fed back to the saccharification process, this feedback fraction is filtered after the saccharification process is completed, even though it has been purified to a certain degree. It turns out. As a result, the amount of saccharified liquid processed in the purification (filtration) step increases, resulting in a heavy burden, and furthermore, it is extremely inefficient to repurify the feedback portion that has already been purified.

It is possible to purify the starch liquefied liquid before saccharification, but due to the characteristics of the starch liquefied liquid, it is necessary to filter it at a relatively high temperature, and such a technology has not been developed to date.

Therefore, an object of the present invention is to provide a method for producing high-purity starch sugar using a membrane fractionation method, in which by-products (dextrin, etc.)
Provides a method for producing high-purity starch sugar, in which the amount of processing in the purification (filtration) process of the saccharified liquid is only slightly increased compared to conventional methods, even though the reflux liquid containing saccharification is fed back to the pre-saccharification process. It's about doing.

[Means to solve the problem]

The present invention comprises (a) a step of pre-saccharifying a starch liquefied liquid, (b)
) step of filtering the partially saccharified liquid obtained by preliminary saccharification, (C)
Main saccharification step of obtaining a saccharified solution by saccharifying the filtered partially saccharified solution; (d) The obtained saccharified solution is subjected to membrane fractionation to produce a reflux solution containing a high-purity starch sugar-containing solution and a polymer dextrin as main components. (e) a step of feeding back the reflux liquid containing polymer dextrin as a main component to the main saccharification step; and (f) a step of feeding back a part of the saccharification liquid containing the enzyme of the main saccharification step or polymer dextrin. The present invention relates to a method for producing high-purity starch sugar, which includes a step of feeding back a part of the reflux liquid, which is the main component, to a preliminary saccharification step.

The present invention will be explained in detail below.

The first step of the method of the present invention is a step of pre-saccharifying the starch liquefaction liquid.

The starch liquefaction liquid used here may be the same as that used in the conventional production of starch sugar. For example, it is obtained by purifying starch from potatoes, Japanese yam, corn, mackerel, etc., and liquefying it with acid or α-amylase.

The enzyme used for pre-saccharification is a starch sugar producing enzyme. There is no particular limitation on the starch sugar producing enzyme (amylase) used in the present invention.

As glucoamylase, glucoamylase derived from fungi such as Rhizopus, Aspergillus, Mucor, Viricararia and the like can be mainly used. Particularly suitable are those originating from Rhizopus delemer. In addition, yeasts such as those of the genus Endomyces, Trichoderma, and Satucharomyces, and those of bacterial origin such as Clostridium acetobutylicum can also be used.

Maltose-producing amylase includes β-amylase derived from plants such as soybean and malt. In addition, Bacillus polymyxa, CBacillus olymvxa, J
.

Robyt, French, Arch, B
iochem, Biophys.

104, 338 (1964)], Bacillus cereus [Bacillus cereus, Y, Takasaki.

Agric, Biol, Chem, 40.15
15-1523 (1976)), Pseudomonas s, S, 5hink
et al., J. Ferment, Technol
,, 53. 693-698 (1975)),
Streptomyces higeloscopicus (Streptomyces hi rosco 1c)
us, Y, Hidaka et al., 5tar
ke, 26. 413 (1974)], Streptomyces plecox
raecox, Wakasei Katsuma et al., Starch Science, 25.15
There are maltose-producing amylases of microbial origin such as 5 (1978) E.

Maltotriose-producing amylases include the following: Katsuma Wakasa et al., Starch Science, 26, 175
(1979), Sprebutomyces φ griseus (S
re tmyces riseus) Origin: Yoshiyuki Takahashi, Abstracts of the 1981 Agricultural Chemistry Conference, p 169
(1983), Bacillus
of genus origin.

Maltotetraose-producing amylases include: J, F, Robyt and R, J.

Ackerman: Arch, Biochem,
Biophys, 145.105 (1971), Pseudomonas stotteri
5 tutzeri) origin.

Examples of maltopentaose-producing amylases include: N, Saito, Arch
, Bioche+n, Biophys, 155
．． 290 (1973), Bacillus licheniformis (
Originated from Bacillus Iichniformis; Kobayashi et al., Abstracts of the 1981 Japanese Starch Society Conference,
p 301 (1983); Yoshigi et al., Abstracts of the 1984 Agricultural Chemistry Conference, p 584 (1984).

Maltohexaose-producing amylases include the following: Second, Kainuma et al., F.
EBS Lett, 26.281 (1972),
Klebsiella pneumonia
pneumoniae) origin; J, F, Ke
nnnedy and C.A., White, 5tarke
, 31°93 (1979); Noguchi et al., Starch Science, 29
．． 107 <1982) Y, Takasaki
i), Agric, Biol, Chem.

47, 2193 (1983').

Pre-saccharification is performed on the starch liquefaction liquid by using an enzyme contained in the reflux liquid from the main saccharification process described below or a part of the reflux liquid containing polymer dextrin as a main component, for example.
It is carried out at a temperature of 60° C. and a pH of 4.0 to 8.5. What is particularly important in the present invention is that preliminary saccharification is
This is to be carried out until the viscosity at °C becomes 5 cp or less. By setting the viscosity of the starch liquefied liquid at 55° C. to 5 cp or less, the starch liquefied liquid can be filtered by a conventional method.

Here, the conditions for pre-saccharification to obtain such results are as follows: use of enzyme I at the level normally employed in the batch method, for example, using 1 to 2 IU of enzyme per 1 g of solid content of raw starch, and for a short period of time. , for example, can be carried out in about 2 hours. As a result, a very small preliminary saccharification tank of about 1/10 to 1/20 is sufficient compared to a saccharification tank for complete saccharification in a normal batch method.

The partially saccharified liquid whose viscosity has been reduced through preliminary saccharification is then filtered. The appropriate filtration method used here is the same as the method conventionally used to filter saccharified liquid. For example, there is a method using a precoat filter or a filter press. When a pre-coated filter is used, diatomaceous earth, perlite, cellulose, activated carbon, etc. are used as a filter aid, and the filtering is carried out at a temperature of 40 to 60°C.

Further, the partially saccharified liquid obtained by preliminary saccharification can be effectively filtered by applying the apparatus described in, for example, JP-A-59-49815, particularly a rotating drum type filter.

The starches used as raw materials for starch liquefaction, such as potato, Japanese bran, corn, and challah mackerel, contain proteins, other nitrogen-containing substances, polyphenols, various salts, tannins,
Contains fat. For example, proteins and nitrogenous substances may react with the product to produce colored substances.

A starch liquefied liquid is usually obtained by adding fresh water to raw starch and liquefying it using an acid or α-amylase. However, the starch liquefied liquid obtained in this way is
Contains the above impurities, albeit in small amounts. For example, polyphenols react with iron to form polymers with large molecular weights, which clog the pores of membranes for membrane fractionation. Therefore, these remaining impurities are removed by the above-mentioned filtration.

Here, one of the features of the present invention is to feed back a part of the reflux liquid containing sugars other than starch sugar (polymer dextrin) from the main saccharification process or the membrane separation process described later to the pre-saccharification process. Despite this, the throughput in the purification (filtration) process of the saccharified liquid is only slightly increased compared to the conventional method.''

As described below, the enzyme concentration in the main saccharification step can be increased to 5 to 10 times or more compared to the normal batch method, while the enzyme concentration in the preliminary saccharification step can be carried out at the same level as the normal batch method as described above. It is possible. Therefore, the starch liquefaction liquid supplied to the preliminary saccharification process is 115 to 1/1
By mixing zero or less reflux, enzyme concentrations comparable to those of conventional batch methods can be achieved. As a result, the throughput of the purification (filtration) step of the pre-saccharified liquid increases only slightly compared to the amount of the liquefied liquid.

Next, in the present invention, the filtered partially saccharified liquid is further saccharified in the main saccharification step.

In the main saccharification step of the present invention, the amount of enzyme added can be increased compared to conventional saccharification methods. In normal batch methods, 1 to 2 IU of enzyme is used per gram of solid content of raw starch, but in the present invention, this can be increased to 5 to 10 IU or more. This is because enzymes are contained in fractions other than starch sugar in the membrane fraction after main saccharification, and are recycled and reused in the main saccharification step.

As a result, the present invention has the advantage that the size of the reaction vessel can be significantly reduced compared to the usual batch method.

In addition, in the present invention, enzymes contained in the reflux liquid other than starch sugar in membrane fractionation are mainly recycled together with the reflux liquid to the main saccharification process, but other than that, enzymes contained in the reflux liquid other than starch sugar are recycled to the main saccharification process. A portion of the liquid (all containing high concentrations of enzymes) is recycled and reused for pre-saccharification.

Thereby, the utilization rate of the enzyme can be increased.

In addition, in the saccharification process (preliminary saccharification and main saccharification) of the present invention, it is preferable to coexist a debranching enzyme in addition to the starch sugar producing enzyme (amylase).

A debranching enzyme is an enzyme that hydrolyzes α-1,6-glucoside bonds in starch. Examples of such substances include prolanases originating from microorganisms such as Bacillus acidopluriticus and Klebschula pneumonia, and isoamylases produced by microorganisms of the genus Pseudomonas and Cytophaga. Most glucose-producing amylases have a pH of 4.0 to 6.0, and most maltooligosaccharide-producing amylases have a pH of 5.0 to 6.0.
Since it has an optimum pH in the range of 8.5, it is preferable to use the debranching enzyme in the same stable and optimum pH range.

The amount of debranching enzyme used is usually 1 to 21 U per 11 U of starch sugar producing enzyme. However, it is also possible to set this value in the range of 5 to 10 IU, if necessary. Since debranching enzymes are considerably more expensive than starch-sugar-forming enzymes,
It is usually not economical to use large quantities. However, as mentioned above, in the method of the present invention, enzymes are used cyclically, so only the amount of inactivated enzymes needs to be replenished, so even such expensive enzymes can be used in large quantities. It can be used for.

The saccharified liquid obtained from the main saccharification step is then subjected to membrane fractionation. An ultrafiltration membrane is used for this membrane fractionation. In order to obtain the target starch sugar such as malto-oligosaccharide with high purity and efficiency, it is preferable to use an ultrafiltration membrane having a molecular weight cut-off of 1000 to 10000. Note that the molecular weight cutoff of the ultrafiltration membrane can be adjusted as appropriate depending on the purity required for the target product.

The starch sugar thus obtained is of high purity.

The reflux liquid, which is fractionated in the membrane fractionation and contains a large amount of dextrin and the like other than starch sugar, is mainly recycled to the main saccharification step. However, a part of the reflux liquid can also be circulated to the preliminary saccharification step.

〔Effect of the invention〕

Although the method for producing high-purity starch sugar using the membrane fractionation method of the present invention feeds back the reflux liquid containing by-products (dextrin, etc.) or a part of the main saccharification process to the pre-saccharification process, the saccharification The throughput in the liquid purification (filtration) process is only slightly increased compared to conventional methods. Moreover,
The starch sugar obtained is of high purity.

Furthermore, in the conventional method, the enzyme was disposable, so
Although it was not economically possible to increase the enzyme concentration,
In the production method of the present invention, since the enzyme can be reused, it is possible to increase the enzyme concentration.

The present invention will be further explained below with reference to Examples.

〔Example〕

α-
Starch liquefaction solution (Brix concentration: 30) using amylase
, DE: 12.8, crude protein content: 0.202%
, crude fat content: 0.127%).

This starch liquefaction liquid was supplied to a 300-liter pre-saccharification tank at 96 i/hr.

On the other hand, in the main saccharification tank of 300 d, Pseudomonas stritzeri (Pseud) was added to the starch liquefaction solution in advance.

360 IU (5,0 IU/g-solid content) of maltotetraose-producing amylase (specific activity 801 U/■ protein) originating from Pseudomonas monas 5 tutzeri and Pseudomonas amyloderamosa (Pse), a debranching enzyme.
720 IU (10.0 IU/g-solid content) of isoamylase originating from S. udomonas am loderamosa was supplied and reacted for 4 hours at a temperature of 40°C and a pH of 7.0 until maltotetraose in the main saccharification tank was 50.5 %
A saccharified solution was obtained.

This saccharification solution was supplied to the preliminary saccharification tank together with the starch liquefaction solution at a rate of 24/hr.

The partially saccharified liquid flowing out from the pre-saccharification tank was then supplied at a rate of 120 d/hr to a pre-coat filter having a filtration area of 0.1 I and using Kenso earth as a filtration agent. The viscosity of this partially saccharified liquid at 55°C was 5 cp.

The partially saccharified liquid obtained from the precoat filter was supplied to the above-mentioned main saccharification tank.

The saccharified liquid flowing out from the main saccharification tank is processed through a cross-flow type ultrafiltration device (molecular weight cut-off of 20
00) at a rate of 1000 mj/hr. Product starch sugar was obtained as a filtrate at a rate of 96 d/hr. On the other hand, the reflux liquid was returned to the main saccharification tank.

Table 1 shows the compositions of the starch sugar in the preliminary saccharification tank and the main saccharification tank and the product starch sugar.

Table 1

Claims (1)

[Claims] (a) A step of pre-saccharifying a starch liquefied solution, (b) A step of filtering a partially saccharified solution obtained by pre-saccharification, (c) A step of saccharifying the filtered partially saccharified solution to obtain a saccharified solution. (d) a step of subjecting the obtained saccharified liquid to membrane fractionation to separate it into a high-purity starch sugar-containing liquid and a reflux liquid containing polymer dextrin as the main component; A step of feeding back the reflux liquid containing dextrin as the main component to the main saccharification process, and (f) pre-saccharification of a part of the saccharification liquid containing enzymes in the main saccharification process or a part of the reflux liquid containing polymer dextrin as the main component. A method for producing high-purity starch sugar, including a step of feeding back to the process.