JP2004345998A

JP2004345998A - Method for rapidly producing amino acid

Info

Publication number: JP2004345998A
Application number: JP2003143962A
Authority: JP
Inventors: Kitain Amand; アマンド・キタイン; Shunsaku Kato; 俊作加藤; Takashi Moriyoshi; 孝森吉
Original assignee: KAGAWA INDUSTRY SUPPORT FOUND; Kagawa Industry Support Foundation
Current assignee: KAGAWA INDUSTRY SUPPORT FOUND; Kagawa Industry Support Foundation
Priority date: 2003-05-21
Filing date: 2003-05-21
Publication date: 2004-12-09

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that in the conventional method for producing an amino acid by hydrolyzing protein, high-concentrated hydrochloric acid is added and reflux is carried out for many hours to hydrolyze the protein or the protein is hydrolyzed at a high temperature of ≥200°C under high pressure for several hours, an unstable amino acid is decomposed due to requirement of long hours for the hydrolysis and a necessary amino acid has difficulty in control and recovery and to establish a technique for efficiently producing a useful amino acid by rapidly hydrolyzing the protein under a mild conditions in comparison with the conventional method. <P>SOLUTION: The method for producing an amino acid mixture is a method for using microwave in hydrothermal decomposition at a high temperature under high pressure so that the protein is rapidly subjected to fractional decomposition only by water at a low temperature of ≤200°C under low pressure of ≤16.5 atmospheric pressure or for using an alkali so that the protein is completely hydrolyzed at a low temperature of 100-110°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】本発明は、動植物系素材及び食品廃棄物などタンパク質を含む素材から組成の異なるアミノ酸混合物を得ることができるアミノ酸混合物の迅速製造方法に関する。
【０００２】
【従来技術】魚のあらや魚粉等の水産加工廃棄物、大豆カスや糠などの食品廃棄物については再利用率を上げ、排出量を削減することが求められている。このような状況で廃棄物を単に焼却あるいは発酵処理するだけでは不十分であり、タンパク質を加水分解して、調味料、医薬品、化粧品、飲料などとして注目されて付加価値の高いアミノ酸へ転換して再利用する技術の研究が進められている。
【０００３】天然素材からアミノ酸を製造する方法として一般に酸加水分解法が用いられてきた。この方法では加水分解するのに長時間加熱処理する必要がある。このため、生成したアミノ酸のうち、熱や酸に不安定なアミノ酸はさらに分解される。
【０００４】また、超臨界水は反応性が高く、有害物質や有機性廃棄物は超臨界水によって極短時間に酸化分解されることから、各種の有害排水や廃棄物の超臨界水酸化による無害化研究が盛んに行われている。この方法では有機性廃棄物が分子量の小さな炭化水素や二酸化炭素まで分解される。
【０００５】超臨界水の反応性を利用してタンパク質を加水分解してアミノ酸やペプチドを製造する研究がなされている（特開Ｈ０９−２６８１６６、特開２００２−０６０３７６）。この方法では高速でタンパク質が分解できることを報告しているが、分解速度が大きく、反応制御が困難で、任意の成分の回収が困難である。
【０００６】また、超臨界水は腐食性が大きく、且つ、無機塩類の溶解性が小さくなるため塩析が起こり、管の閉塞などが問題となるため、様々な研究がなされている。
【０００７】一方、亜臨界の高温高圧水も活性で、触媒なしで、有機化合物を加水分解でき、低分子化できる。これを利用してタンパク質系廃棄物を加水分解してアミノ酸に転換して、再利用する試みがなされている（特開２０００２−３３２２６５、特開２００１−３３２２７２）。タンパク質系材料又はタンパク質系廃棄物を２００℃以上の飽和水蒸気圧下の水熱条件で温度・圧力を変化させて生成するアミノ酸組成を制御する方法が提案されている。
【０００８】魚腸骨のモデル物質として、アジやカツオの魚肉を用いて実験が行われ、２００℃以上の高温高圧水で処理し、アミノ酸（主としてシスチン、アラニン、グリシン、ロイシン）及び数種の有機酸（リン酸、乳酸）などが生成することが報告されている。その際に油状物質も生成し、その中にドコサヘキサンエン酸（ＤＨＡ）やエイコサペンタエン酸（ＥＰＡ）など高付加価値の長鎖の不飽和脂肪酸が含まれていることも報告されている（特開Ｈ１１−３４２３７９）。しかし、この方法では処理温度が高く、処理時間が長く、効率が悪いうえに、温度に不安定なアミノ酸の製造が困難である。これまでに、タンパク質を低温・高速で加水分解して、安定した成分組成のアミノ酸を製造する方法は開発されていない。
【０００９】電子レンジは水などの極性物質を加熱する内部加熱法で、食品の急速加熱法として、一般家庭に広く普及している。電子レンジの利用法としては食品の暖め、調理、膨化、乾燥などである。
【００１０】最近、マイクロ波による著しい化学反応促進効果が認められ、有機合成・分解反応、無機微粒子の合成などが従来の外部加熱による反応に比べ、反応条件の穏和化、反応速度の著しい高速化、反応選択性の向上などが報告されている。
【００１１】高圧密閉容器中に生体材料や鉱物材料を入れ、強酸性下でマイクロ波照射して高温高圧の状態で加熱処理して、試料を分解して溶液化した後、窒素やＴＯＣ分析及びＩＣＰ、原子吸光分析用の試料とする方法が確立されている。従来の分解法に比べ、分解速度が１〜２桁大きくなることが知られており、分析の前処理法として広く利用されている。
【００１２】近年、高圧密閉容器を用いたマイクロ波水熱法で、金属、金属酸化物、硫化物、リン酸塩、複合酸化物等のナノ粒子が高速で得られることが報告されている。
【００１３】
【課題を解決しようとする課題】マイクロ波水熱法を有機化合物、有機金属化合物に適用し、反応速度の著しい短縮、収率、純度及び選択性の著しい向上が報告されているが、簡便な連続反応装置が開発されていないこともあり、連続製造に関する報告はほとんど認められていない。
【００１４】タンパク質を加水分解してアミノ酸を製造する従来法では、高濃度の塩酸を加え、長時間還流して分解する方法、または２００℃以上の高温高圧水中で数時間加水分解するが、加水分解に長時間を要するため、不安定なアミノ酸が分解し、必要なアミノ酸を制御して回収することが困難である。このため、従来法に比べて、穏和な条件で迅速に加水分解し、有用なアミノ酸を効率的に製造できる技術の確立を目指すものである。
【００１５】
【課題を解決するための手段】本発明者らはマイクロ波水熱法によるバイオマスの加水分解による有用成分の回収の研究を鋭意行った結果、マイクロ波水熱法によりタンパク質が通常の水熱法（２００℃以上の飽和水蒸気圧下）に比べて、１５０〜２００℃という低温・低圧条件において短時間に加水分解できること、また、温度制御してアミノ酸を分別回収できる可能性を見出した。
【００１６】さらに、アルカリ性条件では１００〜１１０℃の飽和水蒸気圧下で短時間に加水分解され、原料タンパク質のアミノ酸組成を反映したアミノ酸混合溶液が得られた。
【００１７】従来の水熱分解法では、特開２００２−３３２２６５にあるように、２００℃以上で、且つ、飽和水蒸気圧以上の水で分解する必要があるが、マイクロ波照射すると１５０〜２００の温度で分解できる。絹タンパク質の場合、１５０℃では主としてアスパラギン酸が、１７５℃では主としてセリン、グリシン、アラニンが、２００℃ではグリシンとアラニンが回収でき、温度制御によりアミノ酸組成を制御できることを見出した。
【００１８】アルカリが存在すると１１０℃以下という低温で加水分解でき、低温であるためさらなる分解が起こらず、ほぼ原料組成比で加水分解でき、グリシン、アラニン、セリンが効率よく回収できることを見出したものである。
【００１９】
【発明の実施形態】本発明は高温高圧下での水熱分解にマイクロ波を用いることにより、水のみで２００℃、１６．５気圧以下の低温、低圧の条件で迅速に分別分解できること、アルカリを用いることにより、１００〜１１０℃の低温で、迅速に完全加水分解できるものである。タンパク質源としては絹、羊毛などの他、魚介類、肉類及び植物性の大豆、糠など及びその廃棄物を用いることができる。
【００２０】すなわち、水に所定量タンパク質を加えて、密閉容器に入れ、マイクロ波照射して１５０℃の所定温度で所定時間加熱処理する。冷却後、未分解のタンパク質を回収した後、再度、密閉容器に水にとともに入れ、マイクロ波照射下１７５℃で所定時間処理する。同様の手順で２００℃において分解処理する。絹タンパク質の場合、１５０℃でアスパラギン酸を、１７５℃以上でセリン、グリシン、アラニンを、２００℃でアラニンとグリシンを主成分とするアミノ酸を回収することができる。
【００２１】また、タンパク質と所定濃度のアルカリ水溶液を密閉容器に入れ、１００〜１１０℃の所定温度・所定時間マイクロ波水熱処理を行う。加水分解反応は目標温度（１１０℃）に達した時点においてほぼ終了し、原料のアミノ酸組成比に対応した組成のアミノ酸水溶液を得た。絹フィブロインではグリシン、アラニン、セリンの混合水溶液が得られた。この水溶液を酸で中和した後、透析法あるいは希釈法でアミノ酸混合溶液を得るものである。
【００２２】また、本発明のマイクロ波水熱法では、タンパク質を粉砕したスラリー状とすることにより、マイクロ波オーブン中に設置したチューブラー反応管にスラリーポンプで送液し、連続的に反応させることができる。
【００２３】
【作用】魚介類の廃棄物は腐りやすく、廃棄物処理が嫌われる傾向にある。これらのタンパク源を加水分解して、有用なアミノ酸を製造するものである。従来の水熱分解法では超臨界あるいは亜臨界水における分解が主体である。従来の水熱分解法の分解条件は２００℃、２０気圧以上が必要である。本発明のマイクロ波水熱法で処理すると、水のみでは１５０〜２００℃、アルカリ水溶液を用いると１００〜１１０℃の条件で数分以内の短時間に完全加水分解できることを見出したものである。マイクロ波照射することにより、反応条件が著しく緩和できること、反応速度が著しく大きくなること、熱に不安定なアミノ酸を分解させることなく、回収できることなどの特徴を有している。
【００２４】絹フィブロインをマイクロ波水熱法で分解すると、水のみで加水分解するとアスパラギン酸、セリン、アラニン、グリシンなどを分別回収でき、水のみを使用しているため、不要成分のないアミノ酸混合溶液が回収でき、調味料、健康食品あるいは飲料に用いることが可能である。また、水酸化アルカリを用いると１００℃以上の飽和水蒸気圧下で完全加水分解でき、原料のアミノ酸組成比に対応したアミノ酸組成水溶液が回収できる。この場合、アルカリを酸で中和した後、透析で塩を除去するかあるいは希釈して使用することができる。
【００２５】
【実施例】本発明の実施例及び比較例を以下に示すが、これらは特許請求範囲を限定するものではない。
【００２６】
【実施例１】シルクフィブロイン（岐阜バイオ産業研究所提供）２０ｍｇと脱イオン水１０ｍｌを樹脂製耐熱容器に入れ、高圧マイクロ波反応装置（マイルストーン製：ウルトラクレイブ）に設置し、アルゴンガスで３ＭＰａ程度に加圧した後、マイクロ波（２．４５ＧＨｚ）を所定時間照射して加水分解した。得られた水溶液中のアミノ酸濃度を分析した結果を表１及び図１に示す。マイクロ波水熱分解法では１５０℃では主としてアスパラギン酸が生成し、１７５℃では反応時間が短い場合（３０分）はアスパラギン酸が生成し、反応時間が長くなるとセリン、グリシン、アラニンが生成し、アスパラギン酸は濃度が減少した。２００℃ではグリシンとアラニンが主生成物であった。
【００２７】
【表１】

【００２８】
【比較例１】実施例と同様にシルクフィブロイン（岐阜バイオ産業研究所提供）２０ｍｇと脱イオン水１０ｍｌをステンレス容器のオートクレイブに入れ、電気的に加熱し、所定温度に達してから所定時間保持した後、加熱を止め、冷却して水溶液を取り出し、アミノ酸組成を分析した。結果を表１及び図１に示す。本法では２００℃以下ではほとんど分解せず、２００℃でも１時間加熱処理しても生成アミノ酸量が著しく小さく、マイクロ波水熱法の１／５０以下であった。
【００２９】
【実施例２】シルクフィブロイン２０ｍｇと所定濃度のアルカリ水溶液２０ｍｌを樹脂製耐熱容器に入れ、高圧マイクロ波反応装置に装填して所定温度、所定時間マイクロ波照射した。アルカリ濃度は１規定と６規定、反応温度は１１０と２００℃、所定温度での保持時間を０，３０，６０分として実験を行い、得られた水溶液中のアミノ酸組成を分析した。アルカリ濃度と反応温度を変えて実験した結果を図２に、１１０℃で反応時間を変えて実験して結果を図３に示す。図２の結果から水酸化ナトリウムの濃度が１規定と６規定ではほとんど差がなく、また、処理温度も１１０℃と２００℃では差がないことから、１規定、１１０℃でよいことが分かった。また、図３の結果から、反応温度が１１０℃においては、保持時間に関係なく、いずれも完全に加水分解しており、溶液温度が１１０℃に達すると同時に完全にアミノ酸分解することが分かった。
【００３０】
【比較例２】実施例２と同様に、シルクフィブロイン２０ｍｇと所定濃度の塩酸水溶液２０ｍｌを樹脂製耐熱容器に入れ、所定温度、所定時間マイクロ波照射した。反応温度、酸濃度、反応時間を変えて実験を行った結果を図２、図３に示す。
塩酸を用いた場合は、アルカリに比べ反応性が劣り、１規定では分解率が著しく低かった。水だけでは１１０℃では分解しなかった。
【００３１】
【実施例３】カキの廃棄物を２５０ｍｇと６規定の水酸化ナトリウム水溶液５０ｍｌを樹脂製耐熱容器にとり、１１０℃で３０分間マイクロ波照射した。得られた水溶液のアミノ酸組成を測定した結果、表２に示すようにフェニルアラニン、グリシン、ヒスチジン、リジンなどのアミノ酸が得られた。
【００３２】
【表２】

【００３３】
【発明の効果】以上詳述したように、マイクロ波水熱法ではタンパク質が迅速にアミノ酸に加水分解でき、水のみの場合は１５０〜２００℃で、処理温度を変えることにより、アミノ酸を分別回収することができることが分かった。水のみを用いるため、安全であり、且つ、塩分等を分離精製する必要がなく、食品等にそのまま利用することができる。
【００３４】アルカリの存在下でマイクロ波水熱処理すると、１１０℃以下の温度で短時間に加水分解すること、すなわち、マイクロ波照射して１１０℃に達すると同時にほぼ完全に加水分解していることが分かった。１規定の水酸化ナトリウムの存在下、１００〜１１０℃でほぼ完全に加水分解することを認めた。使用するタンパク質量を増やすことにより高濃度のアミノ酸を回収することができ、中和のみで使用することができる。
【図面の簡単な説明】
【図１】高温高圧水による絹フィブロインの加水分解によるアミノ酸生成についてマイクロ波水熱法と通常の水熱法の比較
【図２】マイクロ波水熱法によるアミノ酸の生成についてアルカリ濃度と反応温度の影響及び酸添加との比較
【図３】マイクロ波水熱法によるアミノ酸の生成に対する反応時間の影響[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rapidly producing an amino acid mixture capable of obtaining an amino acid mixture having a different composition from a protein-containing material such as animal or plant material and food waste.
[0002]
2. Description of the Related Art It is required to increase the recycling rate and reduce the amount of processed fishery waste such as fish ash and fish meal, and food waste such as soybean waste and bran. It is not enough to simply incinerate or ferment the waste in such a situation. It hydrolyzes the protein and converts it to high-value-added amino acids that are attracting attention as seasonings, pharmaceuticals, cosmetics, beverages, etc. Research on technologies for reuse is ongoing.
As a method for producing amino acids from natural materials, an acid hydrolysis method has been generally used. In this method, heat treatment is required for a long time for hydrolysis. For this reason, among the generated amino acids, the amino acids which are unstable to heat or acid are further decomposed.
Further, supercritical water has high reactivity, and harmful substances and organic wastes are oxidatively decomposed by supercritical water in a very short time. Detoxification research is being actively conducted. In this method, organic waste is decomposed into low molecular weight hydrocarbons and carbon dioxide.
[0005] Studies have been made to produce amino acids and peptides by hydrolyzing proteins utilizing the reactivity of supercritical water (JP-A-09-268166, JP-A-2002-060376). Although this method reports that proteins can be degraded at a high speed, the decomposition rate is high, the reaction is difficult to control, and it is difficult to recover any components.
Further, supercritical water is highly corrosive and has low solubility of inorganic salts, so that salting out occurs, which causes problems such as blockage of pipes. Therefore, various studies have been made.
On the other hand, subcritical high-temperature high-pressure water is also active, and can hydrolyze organic compounds and reduce the molecular weight without a catalyst. Attempts have been made to utilize this to hydrolyze protein waste to convert it to amino acids for reuse (JP-A-2000-332265, JP-A-2001-332272). There has been proposed a method for controlling the composition of amino acids produced by changing the temperature and pressure of protein-based materials or protein-based waste under hydrothermal conditions under a saturated steam pressure of 200 ° C. or higher.
[0008] Experiments have been carried out using fish meat of horse mackerel and bonito as a model substance of fish iliac bone, treated with high-temperature and high-pressure water of 200 ° C or more, and amino acids (mainly cystine, alanine, glycine, leucine) and several kinds of It has been reported that organic acids (phosphoric acid, lactic acid) and the like are produced. At that time, it is also reported that an oily substance is formed, and contains high-value-added long-chain unsaturated fatty acids such as docosahexaneenoic acid (DHA) and eicosapentaenoic acid (EPA). Open H11-342379). However, in this method, the processing temperature is high, the processing time is long, the efficiency is low, and it is difficult to produce a temperature-labile amino acid. Until now, no method has been developed for producing amino acids having a stable component composition by hydrolyzing proteins at low temperature and high speed.
A microwave oven is an internal heating method for heating a polar substance such as water, and is widely used in households as a rapid heating method for food. Applications of the microwave oven include heating, cooking, puffing, and drying food.
[0010] Recently, a remarkable chemical reaction promoting effect by microwave has been recognized, and the organic synthesis / decomposition reaction, the synthesis of inorganic fine particles, etc., have milder reaction conditions and a remarkably higher reaction rate than the conventional reaction by external heating. And improvement in reaction selectivity.
A biomaterial or a mineral material is placed in a high-pressure closed container, and the sample is decomposed into a solution by subjecting it to microwave irradiation under strong acidity and heating at a high temperature and high pressure to analyze the sample. A method for preparing a sample for ICP and atomic absorption analysis has been established. It is known that the decomposition speed is one to two orders of magnitude higher than that of the conventional decomposition method, and is widely used as a pretreatment method for analysis.
In recent years, it has been reported that nanoparticles of metals, metal oxides, sulfides, phosphates, composite oxides, and the like can be obtained at high speed by a microwave hydrothermal method using a high-pressure closed vessel.
[0013]
Although the microwave hydrothermal method is applied to organic compounds and organometallic compounds, it has been reported that the reaction speed is remarkably shortened and the yield, purity and selectivity are remarkably improved. Since a continuous reactor has not been developed, there have been few reports on continuous production.
In the conventional method for producing an amino acid by hydrolyzing a protein, a method of adding a high concentration of hydrochloric acid and refluxing for a long time to decompose, or hydrolyzing in high-temperature and high-pressure water at 200 ° C. or higher for several hours, Since the decomposition takes a long time, unstable amino acids are decomposed, and it is difficult to control and collect necessary amino acids. For this reason, the present invention aims to establish a technique capable of efficiently producing useful amino acids by hydrolyzing quickly under mild conditions as compared with the conventional method.
[0015]
Means for Solving the Problems The present inventors have intensively studied the recovery of useful components by hydrolyzing biomass by the microwave hydrothermal method. As a result, the protein was converted to the normal hydrothermal method by the microwave hydrothermal method. (Under a saturated steam pressure of 200 ° C. or more), it has been found that hydrolysis can be performed in a short time under low-temperature and low-pressure conditions of 150 to 200 ° C., and that amino acids can be separated and recovered by controlling the temperature.
Further, under alkaline conditions, hydrolysis was carried out in a short time under a saturated steam pressure of 100 to 110 ° C., and an amino acid mixed solution reflecting the amino acid composition of the raw protein was obtained.
In the conventional hydrothermal decomposition method, as described in Japanese Patent Application Laid-Open No. 2002-332265, it is necessary to decompose with water at 200 ° C. or more and a saturated steam pressure or more. Decomposes at temperature. In the case of silk protein, it was found that mainly aspartic acid could be recovered at 150 ° C, mainly serine, glycine and alanine could be recovered at 175 ° C, and glycine and alanine could be recovered at 200 ° C, and the amino acid composition could be controlled by temperature control.
It has been found that hydrolysis can be carried out at a low temperature of 110 ° C. or less in the presence of an alkali, and further decomposition does not occur because of the low temperature, the hydrolysis can be carried out at almost the raw material composition ratio, and glycine, alanine and serine can be efficiently recovered. It is.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses a microwave for hydrothermal decomposition under high temperature and high pressure, so that it can be rapidly separated and decomposed at 200 ° C. and low temperature and low pressure of 16.5 atm or less with water alone. By using the compound, it is possible to rapidly and completely hydrolyze at a low temperature of 100 to 110 ° C. As a protein source, in addition to silk, wool and the like, fish and shellfish, meat and vegetable soybeans, bran and the like and wastes thereof can be used.
That is, a predetermined amount of protein is added to water, placed in a sealed container, irradiated with microwaves, and heated at a predetermined temperature of 150 ° C. for a predetermined time. After cooling, the undegraded protein is recovered, then put again in water in a closed container, and treated at 175 ° C. for a predetermined time under microwave irradiation. Decompose at 200 ° C. in the same procedure. In the case of silk protein, aspartic acid can be recovered at 150 ° C, serine, glycine, and alanine can be recovered at 175 ° C or higher, and at 200 ° C, an amino acid containing alanine and glycine as main components can be recovered.
Further, the protein and an aqueous alkali solution having a predetermined concentration are placed in a closed container, and microwave hydrothermal treatment is performed at a predetermined temperature of 100 to 110 ° C. for a predetermined time. The hydrolysis reaction was almost completed when the target temperature (110 ° C.) was reached, and an amino acid aqueous solution having a composition corresponding to the amino acid composition ratio of the raw material was obtained. For silk fibroin, a mixed aqueous solution of glycine, alanine and serine was obtained. After neutralizing this aqueous solution with an acid, an amino acid mixed solution is obtained by a dialysis method or a dilution method.
In the microwave hydrothermal method of the present invention, the protein is converted into a slurry by pulverizing the protein, which is then sent to a tubular reaction tube installed in a microwave oven by a slurry pump to continuously react. be able to.
[0023]
[Effects] Fish and seafood waste tends to perish easily, and waste treatment tends to be disliked. Hydrolysis of these protein sources produces useful amino acids. In the conventional hydrothermal decomposition method, decomposition in supercritical or subcritical water is mainly performed. The decomposition conditions of the conventional hydrothermal decomposition method require 200 ° C. and 20 atm or more. It has been found that, when the treatment is carried out by the microwave hydrothermal method of the present invention, complete hydrolysis can be achieved within a short time within several minutes at 150 to 200 ° C. using water alone and at 100 to 110 ° C. using an aqueous alkaline solution. Irradiation with microwaves has the characteristics that the reaction conditions can be remarkably relaxed, the reaction rate can be significantly increased, and the amino acid that is unstable to heat can be recovered without being decomposed.
When silk fibroin is decomposed by the microwave hydrothermal method, aspartic acid, serine, alanine, glycine, etc. can be separated and recovered by hydrolyzing only with water. Since only water is used, amino acid mixing without unnecessary components can be achieved. The solution can be recovered and used for seasonings, health foods or beverages. When alkali hydroxide is used, complete hydrolysis can be performed under a saturated steam pressure of 100 ° C. or more, and an aqueous solution of an amino acid composition corresponding to the amino acid composition ratio of the raw material can be recovered. In this case, after neutralizing the alkali with an acid, the salt can be removed by dialysis or used after dilution.
[0025]
EXAMPLES Examples and comparative examples of the present invention are shown below, but they do not limit the scope of the claims.
[0026]
Example 1 20 mg of silk fibroin (provided by Gifu Bio-Industry Research Institute) and 10 ml of deionized water were placed in a heat-resistant container made of resin, placed in a high-pressure microwave reactor (Milestone: Ultraclave), and 3 MPa with argon gas. After being pressurized to an appropriate degree, microwaves (2.45 GHz) were irradiated for a predetermined time to hydrolyze. The result of analyzing the amino acid concentration in the obtained aqueous solution is shown in Table 1 and FIG. In the microwave hydrothermal decomposition method, aspartic acid is mainly generated at 150 ° C., and at 175 ° C., when the reaction time is short (30 minutes), aspartic acid is generated. When the reaction time is long, serine, glycine, and alanine are generated. Aspartic acid decreased in concentration. At 200 ° C., glycine and alanine were the main products.
[0027]
[Table 1]

[0028]
Comparative Example 1 20 mg of silk fibroin (supplied by Gifu Bio-Industry Research Institute) and 10 ml of deionized water were placed in an autoclave in a stainless steel container, heated electrically, and maintained for a predetermined time after reaching a predetermined temperature, as in the example. After that, the heating was stopped, and the aqueous solution was taken out by cooling, and the amino acid composition was analyzed. The results are shown in Table 1 and FIG. In the present method, it was hardly decomposed at 200 ° C. or less, and the amount of amino acids produced was extremely small even at 200 ° C. for 1 hour, and was 1/50 or less of the microwave hydrothermal method.
[0029]
Example 2 20 mg of silk fibroin and 20 ml of an aqueous alkali solution having a predetermined concentration were placed in a heat-resistant container made of resin, charged in a high-pressure microwave reactor, and irradiated with microwaves at a predetermined temperature for a predetermined time. An experiment was performed with an alkali concentration of 1N and 6N, a reaction temperature of 110 and 200 ° C, and a holding time at a predetermined temperature of 0, 30, and 60 minutes, and the amino acid composition in the obtained aqueous solution was analyzed. FIG. 2 shows the results of an experiment in which the alkali concentration and the reaction temperature were changed, and FIG. 3 shows the results of an experiment in which the reaction time was changed at 110 ° C. and the reaction time was changed. From the results of FIG. 2, it was found that there was almost no difference between the 1N and 6N concentrations of sodium hydroxide, and that the treatment temperature was not different between 110 ° C and 200 ° C. . In addition, from the results in FIG. 3, it was found that when the reaction temperature was 110 ° C., regardless of the retention time, all of them were completely hydrolyzed, and the amino acids were completely decomposed as soon as the solution temperature reached 110 ° C. .
[0030]
Comparative Example 2 In the same manner as in Example 2, 20 mg of silk fibroin and 20 ml of a hydrochloric acid aqueous solution having a predetermined concentration were placed in a heat-resistant container made of resin, and irradiated with microwaves at a predetermined temperature for a predetermined time. FIGS. 2 and 3 show the results of an experiment conducted by changing the reaction temperature, the acid concentration, and the reaction time.
When hydrochloric acid was used, the reactivity was inferior to that of the alkali, and the decomposition rate was extremely low at 1 N. Water alone did not decompose at 110 ° C.
[0031]
EXAMPLE 3 250 mg of oyster waste and 50 ml of 6N aqueous sodium hydroxide solution were placed in a heat-resistant container made of resin and irradiated with microwaves at 110 ° C. for 30 minutes. As a result of measuring the amino acid composition of the obtained aqueous solution, amino acids such as phenylalanine, glycine, histidine and lysine were obtained as shown in Table 2.
[0032]
[Table 2]

[0033]
As described in detail above, in the microwave hydrothermal method, proteins can be rapidly hydrolyzed to amino acids. In the case of water alone, amino acids are separated and recovered by changing the treatment temperature at 150 to 200 ° C. I found that I could do it. Since only water is used, it is safe, and there is no need to separate and purify salt and the like, and it can be used as it is in foods and the like.
When subjected to microwave hydrothermal treatment in the presence of an alkali, hydrolysis occurs at a temperature of 110 ° C. or less in a short period of time, that is, it is almost completely hydrolyzed at the same time as reaching 110 ° C. by microwave irradiation. I understood. Hydrolysis was found to be almost complete at 100-110 ° C in the presence of 1N sodium hydroxide. By increasing the amount of protein used, a high concentration of amino acids can be recovered, and can be used only for neutralization.
[Brief description of the drawings]
Fig. 1 Production of amino acids by hydrolysis of silk fibroin with high-temperature and high-pressure water. Comparison of microwave hydrothermal method with conventional hydrothermal method. Fig. 2 Production of amino acids by microwave hydrothermal method. Effect and comparison with acid addition [Figure 3] Effect of reaction time on amino acid formation by microwave hydrothermal method

Claims

A method for producing an amino acid mixture, comprising hydrolyzing under microwave irradiation when hydrolyzing a protein material to produce an amino acid mixture.

The method for producing an amino acid mixture according to claim 1, wherein the protein-based material is hydrolyzed in hot water at 200 ° C or lower under microwave irradiation.

A method for producing an amino acid mixture by hydrolyzing a protein material at a temperature of 100 ° C. or higher while irradiating microwaves in the presence of an alkali.