JP2007153951A - Method for producing liquefied starchy material and method for producing lactic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a liquefied starchy material through a liquefying treatment of a starchy material by an acid addition process, characterized in reducing agitating mechanical power energy in the reaction and raising starchy material concentration in the liquefying step and also enabling energy cut for cooling in the later-step treatment, and to provide a method for producing lactic acid. <P>SOLUTION: The method for producing the liquefied starchy material by hydrolyzing a starchy material-containing feedstock with lactic acid to effect liquefying the starchy material is provided. In this method, water containing part of the feedstock and the lactic acid is agitated to effect liquefying the starchy material followed by adding the rest of the feedstock to effect the whole starchy material, wherein 0.5 wt.% or more of the lactic acid based on the total weight of the water and the feedstock is used and the liquefaction is carried out until the concentration of the final starchy material comes to 15 wt.% or higher. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing liquefied starch by hydrolyzing a raw material containing rice and other starchy substances with lactic acid, and a method for producing lactic acid using the liquefied starch.

  Polylactic acid is attracting attention as an environmentally-friendly plastic material from the viewpoint of biodegradability, and it is now becoming popular, and simplification of the manufacturing process and reduction of manufacturing costs are indispensable for its diffusion. . Therefore, in order to produce lactic acid as a raw material in large quantities at a low cost, it becomes an indispensable technology for energy saving measures to improve the pretreatment process of fermentation that uses a large amount of heating energy, and to eliminate the energy loss.

  In order to carry out lactic acid fermentation for the purpose of producing a large amount of lactic acid, which is a material for producing polylactic acid, the agricultural products containing rice and other starches as raw materials are heated and boiled to reduce the molecular weight, that is, liquefaction. A pretreatment step of saccharification is required. In this liquefaction treatment, there are mainly two methods, an enzyme addition method and an acid addition method, both of which have been put into practical use.

  In the conventional method, liquefaction is performed by heating at 90 ° C. for about 6 hours using α-amylase in the enzyme addition method. Alternatively, in the acid addition method (lactic acid method), about 1% of the raw material solution is added to reduce the pH of the solution to 3 or less, and the solution is liquefied by heating at 130 ° C. for about 30 minutes (see Patent Document 1). ).

JP-A-8-112097

  However, in the conventional technology, the cost of the processing apparatus in the liquefaction process, the heating energy and the operating cost of the apparatus are expensive, so the production cost of lactic acid as a material for polylactic acid increases, and the use of polylactic acid itself is increased. There is a problem that expansion does not progress easily.

  Therefore, the present inventors have reduced the electric energy consumed by the stirring power in the liquefaction process, reduced the size of the stirring power motor, a control method for reducing operating costs, and the liquid temperature after liquefaction. We have been eagerly studying how to reduce energy consumption.

  In the present invention, the inventors first noticed a rapid increase in the stirring operation power in the gelatinization of starch. This gelatinization phenomenon of starch is a phenomenon in which β-starch in a crystalline state swells together with a hydration bond to change the shape to α-starch in a gel state and becomes a so-called starch paste. In particular, the starchy raw material of rice contains a relatively large amount of branched amylopectin and can be said to be easily pasty.

  Liquefaction treatment is the process of breaking down this starchy starch into low-molecular-weight starch or oligosaccharides, and physical handling such as pumping or biochemical handling such as mixing and stirring in saccharification and fermentation processes. This process is performed for the purpose of improving efficiency. Therefore, as the liquefaction progresses from this pasty state, the starch becomes low molecular weight thanks to the hydrolysis action of lactic acid as an acid, and the power required for stirring operation gradually decreases.

Conventionally, however, a stirrer motor is selected in accordance with the maximum stirrer power required for the starchy gelatinization, and this has been the basis of power design. For this reason, when the molecular weight has been reduced, an oversized motor has been selected and has been in operation.
Therefore, it is the first object of the present invention to make it possible to use a stirrer having a smaller power than conventional ones.

In the conventional method, mixing and liquefaction have been performed as standard processes at a target raw material concentration. Since the above-mentioned starchy gelatinization makes the stirring and mixing operation difficult, in the acid addition method, the upper limit is about 10% of the substrate concentration of the rice raw material. This substrate concentration of 10% is suitable for use as it is for saccharification and fermentation, but in liquefaction and saccharification, heating at 90 ° C or 130 ° C is applied to 90% of water other than the substrate. However, this is not an economical process. In addition, it is necessary to cool the 90 ° C solution in the liquefaction process to 60 ° C in the saccharification process and from 60 ° C to 37 ° C in the fermentation process. . Therefore, the present inventors invented that the raw material concentration is 20% and that the liquid temperature is lowered by adding water at room temperature for cooling.
Therefore, the second problem is to provide an energy-saving technique for achieving this raw material concentration of 20% or more.

  In the conventional method, the stirring and mixing operation becomes difficult due to the increase in liquid viscosity accompanying the gelatinization of the above-mentioned starch at a raw material concentration of 10%, and thus liquefaction treatment at a higher concentration has not been performed. Therefore, in order to obtain a starchy solution having a concentration of 15%, the present inventors first added the raw material in two parts while observing the change while detecting the stirring power situation, and a 20% concentration. In order to obtain this starchy solution, it has been invented that it is added in three portions, and the conditions and methods have been studied.

  In addition, in order to further reduce the operating power in stirring and mixing of starch solutions having a concentration of 15% or more, the operating power is detected by a torque meter, and the measured value is fed back during the stirring and mixing operation. A control method was also studied.

  That is, the present invention reduces the kinetic energy of stirring during the reaction in the liquefaction treatment by the acid addition method of starch, increases the starch concentration in the liquefaction step, and further, energy for cooling in the subsequent treatment. It is an object of the present invention to provide a method for producing a liquefied starch and a method for producing lactic acid that can reduce the amount of lactic acid.

  In order to solve the first problem, it is necessary to obtain conditions that reduce the power required for stirring during starch gelatinization. Therefore, the present inventors have intensively studied the influence on the power due to the decrease in starch concentration and the concentration of lactic acid added. As a result, the lactic acid addition concentration is kept constant, the amount of starch added at the initial stage is reduced, and when the reduced amount is further reduced from the maximum load during starch gelatinization, the maximum amount of stirring is required. It was observed that the power and overall operating power were greatly reduced, and the total amount of stirring energy could be reduced.

Therefore, in order to establish a more specific method, an attempt was made to determine a starch concentration of 15%, which was conventionally impractical, as the final concentration, and add it in two portions. Since this was a good result, the starch concentration of 20% was determined as the final concentration and added in three portions.
As a result, it was found that the maximum required power required for the stirrer was 1/3 or less, and a method for the first problem was established.

As for the second problem, as described in the solution of the first problem, even if the final concentration is high, the amount of starch added is divided, and when liquefaction after gelatinization has progressed, additional addition As a result, the target starch concentration of 20% was obtained.
In other words, in the liquefaction process, the starchy substrate is diluted 10 times, but by diluting it 5 times, it leads to a large reduction in water addition, and the heat energy required for liquefaction of that amount is reduced. Reduced.

  In addition, since the conventional method of applying the stirring power in the liquefaction treatment was to maintain the operation in accordance with the maximum required power, the operating cost of supplying electricity with the stirring power even if liquefaction progresses. Did not decrease. Therefore, the present inventors have invented a method of applying feedback control to the stirring power according to the output signal from the torque meter that has measured the power in the present invention. As a result, it has become possible to reduce the power energy, that is, the electricity supply, which has been unnecessarily applied with stirring power until now.

  In the conventional method, there is an adjustment step of reducing the liquid temperature at 60 ° C. after saccharification treatment to 37 ° C. using cooling water through a cooling heat exchanger before lactic acid fermentation. Not only is it necessary to provide a cooling water supply facility and a heat exchanger for this process, but a cooling adjustment tank may be provided for this purpose. Therefore, the present inventors consider the adjustment of the decrease in the liquid temperature by simply adding water at room temperature, and the starch concentration is set to 20% in the liquefaction / saccharification process which is the pre-treatment of this adjustment process. Later, he invented a method of adding water to make the concentration 10% suitable for fermentation.

  For example, if there is a solution at 60 ° C with 100 liters of 20% substrate, it is a treatment to add 100 liters of water to dilute to 10% substrate, and if the added water is 20 ° C, there is no heat dissipation As a result, 200 liters of 40 ℃ liquid will be completed.

  With the aim of simplifying the manufacturing process and reducing manufacturing costs, in order to manufacture polylactic acid, which is attracting attention as an environmentally-friendly plastic material from the standpoint of biodegradability, the purpose is to manufacture lactic acid in large quantities at low cost. The inventors of the present invention have intensively studied about reducing the production cost by improving the pretreatment process of fermentation that uses a large amount of heating energy.

That is, the method for producing a liquefied starch according to the present invention is a method for producing a liquefied starch by hydrolyzing a raw material containing starch with lactic acid, and stirring the raw material and water containing lactic acid. After liquefying, the raw material is added and stirred to liquefy.
As the raw material containing starch, rice, wheat, corn and other agricultural products are preferable.
In the method for producing a liquefied starch according to the present invention, it is preferable to use 0.5% by weight or more of lactic acid with respect to the total weight of the raw material and water and perform liquefaction until the starch concentration is 15% or more. The amount of lactic acid added is particularly preferably 1.0% by weight or more based on the total weight of the raw material and water. The liquefaction is particularly preferably performed until the starch concentration is 20% or more.

Further, the method for producing a liquefied starch according to the present invention comprises stirring the water containing the raw material and lactic acid using a stirrer, detecting the magnitude of the load applied to the stirrer during stirring, It is preferable to perform feedback control of the power of the stirring device in accordance with the size of the agitator.
In the method for producing a liquefied starch according to the present invention, the water containing the raw material and lactic acid is stirred using a stirrer, the magnitude of the load applied to the stirrer during the stirring is detected, and the magnitude of the load Depending on the situation, the raw material may be added and stirred. The addition of the raw material can be automated by a raw material quantitative supply device.
For the magnitude of the load, it is preferable to connect a torque meter to the motor of the stirring blade of the stirring device and use the value of the rotational torque detected by the torque meter.

The method for producing lactic acid according to the present invention is characterized in that lactic acid is produced from liquefied starch produced by the above-described method for producing liquefied starch by lactic acid fermentation.
In the method for producing lactic acid according to the present invention, it is preferable to lower the liquid temperature by adding water at room temperature to the liquefied starch before the lactic acid fermentation of the liquefied starch.

  In the present invention, to obtain a condition to reduce the maximum required power for the stirrer selection which is the first problem, corresponding to the reduction of the heating energy by raising the starch concentration, which is the second problem, It is possible to provide a method of operation control that can cope with reduction of cooling energy and leads to reduction of stirring power energy. According to the present invention, it is possible to reduce electric energy consumed by stirring power in the liquefaction processing step, to reduce the size of the stirring power motor, to control the operation cost, and to adjust the lowering of the liquid temperature after liquefaction. Energy saving is possible. As a result, waste of electric energy and heat energy can be suppressed and the production cost of lactic acid can be reduced, which can greatly contribute to the spread of polylactic acid, which is a biodegradable plastic that is good for the environment.

  According to the present invention, the electric energy consumed by the excessive stirring device in the conventional method, the reduction of energy that was not required for the object to be stirred, the heat energy that was heating the water that was added in large quantities In addition, it is possible to provide an effective means for reducing the cooling energy used for cooling the saccharified solution. As a result, it is possible to reduce the manufacturing cost of lactic acid, which is a raw material for polylactic acid, which is a biodegradable plastic that is currently in widespread use, and to contribute to expanding the use of biodegradable plastic materials that are good for the environment.

Hereinafter, the present invention will be described more specifically with reference to examples.
However, the technical scope of the present invention is not limited by the following examples.
(Explanation of test equipment)
As shown in FIG. 1, the test apparatus is provided with four baffle plates 2 on the side of a 500 ml separable flask 1 and a small Max Blend blade 3 (manufactured by Sumijuki Equipment System Co., Ltd.) as a stirrer. It is made up of. With this test apparatus, the Max Blend blade 3 was rotated by the motor 4 and stirred at 180 rpm. The motor 4 is provided with a rotation control device 5. The rotation control device 5 can increase or decrease the number of rotations of the motor 4.

  Moreover, in order to raise the temperature to 90 ° C., the flask 1 was immersed in an oil bath 6 filled with cooking oil. The temperature of the cooking oil inside the hot tub 6 was measured with a thermometer 7. Further, in order to measure the stirring power, a torque meter 8 (1200 RTE, model, manufactured by Haydon Co., Ltd.) was connected to the motor 4 of the stirrer, and the rotational torque was continuously detected and recorded during the test. In addition, a rotational viscometer (“Visco Basic” manufactured by Viscotech Co., Ltd.) was used for viscosity measurement.

  In this example, low-glutelin rice “Chunyo” produced in Fukushima Prefecture in 2004 was milled into white rice and then ground and dried to 1 mm or less as a starch raw material. A predetermined amount of water was added to the raw material, and 1% by weight of lactic acid was added to the total weight of the raw material and water.

Implementation conditions are as follows: (1) While stirring at 90 ° C for 3 hours, with a target of 15% starch concentration, the initial concentration is 10%. , The concentration to be added is 5%. (2) Next, the initial concentration is 7.5%, and when the measured value of the torque meter is stabilized, additional addition is performed, and the concentration to be added is 7.5%.
(3) Targeting a starch concentration of 20%, the initial concentration is 10%, and when the measured value of the torque meter is stabilized, additional addition is performed, and the concentration to be added is 10%. (4) Next, when the initial concentration is 7.5%, additional addition is made when the measured value of the torque meter is stable. The additional concentration is made 7.5%, and when the measured value of the torque meter is stabilized, additional addition is made. The concentration is 5%.

(5) For comparison control, the mixture was stirred at 90 ° C for 3 hours at a starch concentration of 15%. And (6) Stirring at 90 ° C. for 3 hours at a starchy concentration of 20%.
The test was conducted under the above six conditions.

The test results of the examples are shown in Table 1, and the fluctuation of the stirring power is shown in FIG. 2 (final concentration 15%) and FIG. 3 (final concentration 20%).

From the results shown in Table 1, it was found that when the starch concentrations were divided and added to both final concentrations of 15% and 20%, the final viscosity and the total energy consumed for stirring were reduced, and the stirring energy was reduced. First, when paying attention to the final viscosity of 15%, the final viscosity is smaller by adding 10% and 5% than by dividing into 2 equal parts and adding 7.5% twice. However, the energy consumption for stirring is smaller in two. This can be presumed to be because, when 10% is added, a larger stirring energy is required than when 7.5%, and when the amount consumed is added, the effect is greatly increased.
Next, paying attention to the final viscosity of 20%, if it is added at 1 degree, it is a viscosity that exceeds the measurement upper limit of the viscometer, but the final viscosity can be obtained by dividing into 2 equal parts and adding 10% twice. As a result, the energy consumed for stirring is reduced to a quarter. In the method of adding 7.5% to 2% in 5 times, the final viscosity is further lowered, but the energy consumption is not much different from 2 parts.
Thus, it was found that the addition method in which the raw material was divided had a great labor saving effect in terms of stirring energy.

  Referring to the graph of FIG. 2 (final concentration 15%), it can be clearly seen how large the power required for stirring when applied at one time is. A power agitator with sufficient margin for this maximum value is selected at the time of design.

That is, in the case of one degree of 15% 0.8kw / m ^3, if 10% + a 5% 0.2kw / m ^3, a 0.1 kw / m ³ if 7.5% + 7.5%. If a stirrer with this capacity is always in operation, a difference in energy consumption corresponding to the number of kw will occur. In addition, if the consumption of stirring power is stable, the effect of stirring is higher than that of power, and an easy mixed state is created.

Referring to the graph of FIG. 3 (final concentration 20%), considering the selection of the stirrer as described above, 20% is 1.6 kw / m ³ if 1 degree and 0.25 if 10% + 10%. If kw / m ³ , 7.5% + 7.5 + 5%, 0.2 kw / m ³ is obtained. Even if the final starch concentration is the same, it can be said that the magnitude of the agitator power is different by a factor of 8 is a great difference not only from the viewpoint of the energy consumption cost but also from the viewpoint of the apparatus cost.

  In the test device, the detected value of the torque meter 8 can be fed back to the rotation control device 5, and the motor 4 of the stirring device can be feedback controlled in accordance with the detected value. Such automation can save labor for stirring energy.

It is a schematic explanatory drawing which shows the test apparatus used in the Example of this invention. It is a graph which shows the fluctuation | variation of the stirring power in the case of 15% of final concentration of the test apparatus used in the Example of this invention. It is a graph which shows the fluctuation | variation of the stirring power in the case of 20% of final concentration of the test apparatus used in the Example of this invention.

Explanation of symbols

1 separable flask 2 baffle plate 3 max blend wing 4 motor 5 rotation control device 6 oil bath 7 thermometer 8 torque meter

Claims (6)

  A method for producing a liquefied starch that hydrolyzes a raw material containing starch with lactic acid, and liquefies the raw material and water containing lactic acid. A process for producing a liquefied starch, characterized in that   The method for producing a liquefied starch according to claim 1, wherein 0.5% by weight or more of lactic acid is used with respect to the total weight of the raw material and water, and liquefaction is carried out until the starch concentration is 15% or more.   Stirring the raw material and water containing lactic acid using a stirrer, detecting the magnitude of the load applied to the stirrer during stirring, and performing feedback control of the power of the stirrer according to the magnitude of the load The method for producing a liquefied starch according to claim 1 or 2, wherein the method is carried out.   Stirring the raw material and water containing lactic acid using a stirrer, detecting the magnitude of the load applied to the stirrer during stirring, and adding the raw material according to the magnitude of the load and stirring The method for producing a liquefied starch according to claim 1, 2, or 3.   A method for producing lactic acid, comprising producing lactic acid by lactic acid fermentation from a liquefied starch produced by the method for producing a liquefied starch according to any one of claims 1 to 4. 6. The method for producing lactic acid according to claim 5, wherein water temperature at normal temperature is added to the liquefied starch before the lactic acid fermentation of the liquefied starch.

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