JPS6128396A - Preparation of lactate - Google Patents

Abstract

PURPOSE:To separate lactic acid from an immersed solution, by subjecting the immersed solution which is produced as a by-product in preparation of starch by milling maize in a wet state to ultrafiltration, concentrating prepared filtrate to crystallize a lactate. CONSTITUTION:In a wet milling method wherein maize is immersed in a dilute aqueous solution of sulfurous acid, the immersed solution contains lactic acid which is produced by homogenous lactic acid fermentation of eoluted soluble saccharide with lactic acid bacteria. A base is added to the immersed solution, which is adjusted to 5-12 PH, flocculate and precipitate are removed from the solution, which is subjected to ultrafiltration. The prepared filtrate is concentrated to crystallize a lactate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing lactate from a soaking liquid produced as a by-product during the production of starch by wet milling corn.

Technical background Soaking liquid (corn, steep liquor, C0rn
5teep liq:uor, hereinafter referred to as O8L. )
is a liquid having a solid content concentration of 3 to 9% by weight, a lactic acid concentration of 1 to 4% by weight, a yellowish brown color, and a mushy odor.

In wet milling of corn for the purpose of producing starch, the initial soaking process reduces the corn to σ, 1-
The corn is immersed in a 0.3 wt. dilute aqueous sulfite solution (liquid mixture at about 50°C) for about 2 days to make it easier to separate the starch granules from the corn. In the soaking process, lactic acid bacteria perform homolactic acid fermentation on soluble sugars eluted from the corn into the dilute aqueous sulfite solution, resulting in O8L containing lactic acid.

In addition to the lactic acid and residual sugar from lactic acid fermentation, OS and L contain proteins, peptides, amino acids, ammonia, starch, pectin, and their hydrolysates from corn, phytic acid, inorganic substances, and trace amounts of vitamins. The analyzed values are shown in Table 1.

Table 1 Analysis value of O8L Generally, this O8L#'i, triple effect can has a moisture content of 60%.
It is concentrated to ~45% by weight and used for feed or fermentation media.

Lactic acid is an oxycarboxylic acid represented by the structural formula OH30HOI-1-000H, and is an organic acid with uses such as food, medicine, and industrial raw materials. It is manufactured using a synthetic method using nitrile as a raw material.

When lactic acid is generally produced by a fermentation method using starch as a raw material, the concentration of the raw material (sugar concentration in the medium) is 20%.
It is concentrated at a high concentration of less than - However, in the corn soaking process, the concentration of sugar eluted from the corn particles into the dilute sulfite aqueous solution is as low as 4% by weight, and various components other than sugar, including proteins, are eluted. ,
Because it coexists with lactic acid, the technology for separating lactic acid from O8L is different from the general fermentation production technology for lactic acid.

Currently, O8L is used as a nutrient for culture media during the fermentation production of antibiotics, etc., and most of it is added to corn husks produced as a by-product at the same time as O8L. It is only used in the production of high protein feed [gluten feed] and has 0
Although 8L contains 20-35 t/1002 solids of lactic acid, no attempt has been made to separate the lactic acid. The development of a technology to separate lactic acid from O8L has been an important issue in related technical fields, but because it is difficult to separate it from fractions other than lactic acid that coexist in O8L,
The useful lactic acid contained remained unutilized.

(Technical Problems Related to the Present Invention) In order to selectively separate O8L and silactic acid, the present inventor first attempted a separation method using an ion exchange resin. This method is a known method in analytical technology, such as ion exchange resin chromatography using an anion exchange resin, which is applied to carboxylic acid analyzers. However, in addition to lactic acid, O8L contains large amounts of anions such as nonmetallic ions, phytic acid, and amino acids, and no ion exchange resin has been developed to separate only lactic acid. Due to contamination of the resin, a large amount of wastewater containing BOD is generated, and an economical separation method using ion exchange resin could not be found.

The present inventor next investigated an esterification method for the purpose of separating O8L and silactic acid. In other words, by applying a general esterification method, methyl lactate or ethyl lactate was separated by live distillation using a sulfuric acid catalyst, but the esterification efficiency was poor due to the effects of coexisting water-soluble proteins and other factors, and a large amount of thermal energy was required. Due to the esterification method, an economical separation method could not be found.

Next, the present inventors conducted extensive research by treating 08L using an ultrafiltration membrane for the purpose of separating lactic acid.

As a result, O8L contains water-soluble polymers of various molecular weights, and when concentrated without any treatment, specific proteins form a storage colloid around lactate crystals, and lactic acid Although it was impossible to selectively separate only 08L, the present inventors removed the water-soluble polymer contained in 08L from the system using an ultrafiltration membrane.
We have found that it is possible to crystallize and separate lactic acid. Analysis of both the ultrafiltered permeate and non-ultrafiltered C8L revealed that among the water-soluble polymers of various molecular weights that unexpectedly coexist during the crystallization and separation of lactic acid, the molecular weight range and hindrance were identified. Furthermore, if the water-soluble polymer has a molecular weight range that does not cause any hindrance, even if a large amount coexists, if a specific protein does not coexist, there will be no hindrance to crystallization separation. It turned out that it wasn't. In other words, in order to selectively crystallize and separate only lactic acid from C8L, it is not necessary to separate and remove substances in the high molecular weight range from C8L to C8L, and only remove specific proteins that interfere with crystallization and separation. It turned out that I should do it.

Purpose of the Invention The purpose of the present invention is to solve the following problems:
The present invention provides a method for producing lactic acid from 8L, and will find a new use for C8L as a raw material for producing lactic acid on an industrial scale.The present invention produces starch by wet-milling corn. lactic acid, which is characterized in that the immersion liquid produced as a by-product is ultrafiltered, and then the obtained ultrafiltration membrane permeate is a-condensed to a solid content concentration of 10 to 70 parts by weight to crystallize lactate. This is a method for producing salt.

Further, the present invention further provides a method of adding a base to a soaking liquid that is produced as a by-product when wet milling corn to produce starch.
The H value is adjusted to 5 to 12, and the agglomerated or precipitated contents are separated as solids, and the obtained soaked a liquid is ultrafiltered.Then, the obtained ultrafiltrate is reduced to a solid content concentration of 10 to 70% by weight. This is a method for producing lactate, which is characterized by crystallizing it as lactate by concentrating it into lactate.

The present invention is characterized by the presence of high-molecular organic substances, such as proteins such as alnomine and globulin, as well as starch, dextrin, hemicellulose, and pectin, which act as positive hindrances when concentrating C8L and crystallizing the lactic acid contained therein. Polysaccharides are efficiently removed in advance using an ultrafiltration membrane, and then the ultrafiltration permeate is reduced to a solid content concentration of 1.
If concentrated to 0 to 70% by weight, lactic acid will crystallize and can be easily separated from the mother liquor by a general solid-liquid separation method such as centrifugation.

aSL, which is produced as a by-product during wet milling of corn, contains various high-molecular organic substances as mentioned above, which are difficult to remove by physical operations such as centrifugation or biological operations such as enzymatic treatment. Chemical operations such as hydrolysis using mineral acids require a large amount of energy, making them unsuitable for industrialization.

Therefore, in the present invention, these high-molecular organic substances contained in C8L are ultrafiltered in the first step, and after removing the high-molecular substances by force if they become an obstacle when crystallizing lactic acid in the next step, By ramming the ultrafiltration membrane permeate in two steps, it has become possible to crystallize lactic acid and separate it from the mother liquor very easily.

(Ultrafiltration membrane) The types of the ultrafiltration membrane used in the present invention are general flat membrane type,
It may be of any type, such as a hollow fin type, a tubular type, or a cylindrical type.

The type of membrane used in the present invention has a nominal molecular weight cutoff of 1.000.
If a membrane with a relatively large nominal molecular weight cutoff is used, the filtration rate of C8L will increase, but the purity of the obtained lactate will decrease; If a relatively small membrane is used, the filtration rate will be low and the purity of the lactic acid obtained will be high, but the membrane area will need to be increased.

(Pretreatment of C8L with a base) Before treating C8L with an ultrafiltration membrane, as a pretreatment, a base such as caustic soda, ammonia, or calcium hydroxide is added to C8L to adjust the pH value to 5 to 1.
2, and after solid-liquid separation of coagulated or precipitated substances, the resulting clear liquid is treated with an ultrafiltration membrane, the filtration rate increases by about 20% or more.

(Solid Content Concentration) Solid content concentration refers to the value obtained by subtracting the evaporation loss (weight %) by 100 when drying at 105° C. for 6 hours.

(Concentration of ultrafiltration membrane permeate liquid) In the present invention, the degree of concentration of the ultrafiltration membrane permeate liquid obtained by ultrafiltration of O8L is 10 to 70% by weight, preferably 40 to 60% by weight solid content. shall be.

Concentration to 70% by weight or more increases the viscosity of the ultrafiltration membrane permeate and increases the amount of O8L adhering to the crystallized lactate crystals, which is undesirable because the yield of crystals during washing decreases.

(Chemical composition of lactate) In the present invention, the chemical composition of the lactate that crystallizes mainly consists of magnesium lactate and calcium lactate.

If necessary, the lactic acid salt obtained by the present invention is used to produce a lactic acid aqueous solution according to a conventional method and used for foods, medicines, industrial raw materials, and the like.

Hereinafter, the present invention will be explained in more detail using experimental examples and examples, but the present invention is not limited thereto.

Experimental Example 08L (solid content concentration 6.7% by weight, lactic acid concentration 1.6% by weight) was subjected to ultrafiltration at its original concentration.

Romicon ultrafiltration device 11.0M100N NOD
Ultrafiltration membrane HF'1.1-43-P on ELHFXS-MKU (hollow fin type, total membrane area 0.1d)
15 permeate obtained by treating 20A of the 08L (denoted as A solution in FIG. 1) using MIO (nominal molecular weight cutoff 10,000) (denoted as B solution in FIG. 2) and 51 concentrated solution (denoted as C solution in FIG. 3) was obtained.

The elution patterns of liquids A, B, and C obtained by gel filtration fractionation with water are shown in FIGS. 1 to 3, respectively. The column used was Sephadex G-50 fine, inner diameter 15U.
x length 10100O, elution amount was 50ml/Hr, and detection was performed at wavelength λ = 280 mix.

As a result, the protein peak associated with gel chromatodarum Pl in solution A was not observed in solution B, and it was determined that a portion of the high-molecular organic matter in O8L was indeed removed by gel fractionation.

Even if liquids A and C are concentrated, their viscosity only increases and no lactate crystals are obtained, but liquid B provides concentrated crystals of lactate.

Divide the above solution B into seven equal parts, each with a solid content concentration of lo.

The crystal yields of the lactate obtained were analyzed and shown in Table 2.

Table 2 When separating the lactic acid contained in Cl5L, the proteins that form storage colloids and impede the growth of lactate crystals are listed in Table 1.
It was surprisingly found that the specific protein indicated by P1 in the figure and the protein indicated by P2 did not impede the growth of lactate crystals.

Furthermore, the results of measuring the infrared absorption spectrum of the liquid obtained by treating the crystals obtained in this experimental example with an ion exchange resin are shown in FIG. 6, and the infrared absorption spectrum of lactic acid is shown in FIG. (
A Hitachi 260 infrared spectrophotometer was used. ) As a result, the infrared absorption spectra in FIGS. 6 and 7 matched, and it was confirmed that the crystals obtained in this experimental example were lactate.

Example 1 O8L (solid content concentration 7.1% by weight, lactic acid concentration 2.1% by weight) was used in an ultrafiltration device manufactured by Romicon, using an ultrafiltration membrane of PMlo (nominal molecular fraction 310,000). and filtered at room temperature.

Assuming the supply pressure to the ultrafiltration membrane as l Kg G/crl
The O8L/207 was fed into the apparatus in a batch manner to obtain 181 of a colorless transparent permeate. When the liquid was concentrated under reduced pressure to a solid content of 45% by weight, crystals 1041 were obtained.

When the crystals were methyl esterified and silactic acid methyl ester was identified and quantified by gas chromatography,
The content of lactic acid (COHsOHOH-COOH) was 87% by weight. The analysis of this lactic acid methyl ester is F,1
．． Analysis method using a Hitachi Model 163 gas chromatograph equipped with a D detector equipped with a separation column (inner diameter 3 mm x length 2 m) filled with Rheoplex #400 (sold by Gask Yotsu Kogyo Co., Ltd.) and using acetophenone as the internal standard. The chromatograms obtained are shown in FIGS. 4 and 5.

FIG. 4 shows a chromatogram of methyl ester prepared from the crystals obtained in this example, and FIG. 5 shows a chromatogram of methyl lactate prepared from the reagent lithium lactate. Peak B in Figures 4 and 5 is the peak of the internal standard (acetophenone); peak A in Figure 5 is the peak of lactic acid methyl ester;
Peak X in the figure can also be determined to be a peak of lactic acid methyl ester. Based on these results, it is confirmed that the crystals obtained in this example are lactate.

Example 2 Using 0SL (solid content concentration 6.6% by weight, lactic acid concentration 2.3% by weight), before treating the O8L with an ultrafiltration membrane, 25% caustic soda was added as a pretreatment. Use p
Table 3 shows the ultrafiltration rate of the treated solution obtained by adjusting the H value to 7.0 and filtering out coagulated or precipitated substances.

The same model of ultrafiltration device as in the experimental example was used.

Table 3: 1. Permeate 2 obtained by filtering O8L pretreated by H adjustment through an ultrafiltration membrane with a nominal molecular weight cutoff of 200,000! Concentrate and expand to a solid content concentration of 45% by weight,
Crystal 629 was analyzed in the same manner as in Example 1 and found to contain 88% by weight of lactic acid. Similarly, in the case of 08L without pretreatment, crystal 64? and lactic acid is 8
Contains 8 weight t% fc.

Example 3 Next, an experimental example regarding the molecular weight cutoff of an ultrafiltration membrane will be shown.

08L (solid content concentration 7.5% by weight, lactic acid concentration 2.0% by weight) is adjusted to pH 9.0 with caustic soda in advance, and the treated liquid obtained by filtering the contents that coagulate or precipitate is supplied to the device. It was made into a liquid.

Nominal molecular weight cutoff 1,000.2,000.10,000
.

50.000, 200,000 and 1,000,0
A comparative test of lactate crystallization was conducted using six types of 00 filtration membranes. Add 2 of the above feed solutions to each device equipped with a membrane.
0! 1 Bl of ultrafiltration permeate was obtained at a time, and the permeation flow rate at that time is shown in the second column of Table 4. The ultrafiltration permeate obtained using six types of membranes was concentrated under reduced pressure to a solid concentration of 45% by weight, and after crystallizing lactate, it was separated in a furnace and a small amount of crystals was collected. Wash with water, dry and weigh the 4th
Shown in the third column of the garment.

The total nitrogen of the obtained crystals was analyzed using the Kjeldahl method, and the fourth
Shown in column 4 of the table.

From the results shown in Table 4 above, it can be seen that the nominal molecular weight cut off of the ultrafiltration membrane used does not have a significant effect on the yield of lactate.

However, when the nominal molecular weight cutoff of the membrane is 200 and O'OO or more, the p overflow rate is 30 no/Hr, rr? However, on the other hand, the total nitrogen content in the crystallized lactate is not high, which indicates that the amount of protein contained in the crystals is increased. As the amount of impurities such as protein increases, the burden on the lactate purification process increases, so the lactic acid separation and production process should be determined in consideration of both the ultrafiltration process and the lactate purification process.

That is, the molecular weight cutoff of the ultrafiltration membrane should be determined in consideration of the desired purity of lactic acid, but generally a membrane with a nominal molecular weight cutoff of about 10,000 to 50,000 is preferable. In this case, either an industrial continuous membrane treatment or a batch membrane treatment can be used efficiently, and the membrane type should preferably be a hollow fin type or a tubular type, taking cleaning and contamination into consideration. In addition, O is the feed liquid during ultrafiltration treatment.
The liquid temperature of 8L etc. may be at room temperature and there is no need to heat it.

Effects of the Invention According to the present invention, O8L, which contains useful substances but whose use was mostly limited to feed,
This opens up its use as an industrial raw material for the production of lactate, and wet milling plants of corn can have great economic benefits.

[Brief explanation of the drawing]

FIG. 1 is a four-madogram of liquid A glue in an experimental example. FIG. 2 is a chromatogram of the B solution of the experimental example. FIG. 3 is a chromatogram of the O solution in the experimental example. FIG. 4 is a chromatogram of the methyl ester prepared from the crystals obtained in Example 1. FIG. 5 is a chromatogram of lactate methyl ester. FIG. 6 is an infrared absorption spectrum of lactic acid from lactate obtained in an experimental example. FIG. 7 is an infrared absorption spectrum of lactic acid. Applicant Oji Cornstarch Co., Ltd. Representative Patent Attorney Minoru Isaka Mistakes Figure 1 Elution amount (mA) Figure 2 Figure 3 Elution amount (mt) Figure 4 Figure 5 Non-retention time IJJ
Retention time L minutes] Figure 6 Wave number (cm-1) Figure 7 Wave number (cm”) Procedural amendment August 22, 1985

Claims (2)

[Claims] (1) Ultrafiltration of the soaking liquid that is produced as a by-product when wet milling corn to produce starch, and then concentrating the obtained ultrafiltration membrane permeate to a solid content concentration of 10 to 70% by weight. A method for producing lactate, characterized by crystallizing it as lactate. (2) Add a base to the soaking liquid that is a by-product when wet milling corn to produce starch, adjust the pH value to 5 to 12, and separate the contents that aggregate or precipitate. A method for producing lactate, which comprises ultrafiltration and then concentrating the obtained ultrafiltration membrane permeate to a solid content concentration of 10 to 70% by weight to crystallize it as lactate.