Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1988-01-27
1989-10-17
Reamer, James H.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
562516, C07C 9902
Patent
active
048748935
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a new industrial process of hydrolysis of proteins for the extraction of amino-acids.
The extract of amino acids contained in proteins by hydrolysing the latter with strong inorganic acids is already known.
In order to ensure the breaking of peptide linkages of proteins and the formation of the corresponding amino acids with a good yield, it is essential that this acid has a pKA less than or equal to -2.
However, this strong acid must not bring about a degradation of the amino acids formed during the hydrolysis reaction. Some of these amino acids are unstable in a concentrated acid medium and the excess of this acid must be easy to remove from the reaction mixture after hydrolysis.
Conclusive results have been obtained in this respect in the laboratory, with aqueous solutions of hydrochloric acid, the pKA of which is -7, at a concentration of approximately 6N and at a temperature equal to or greater than 100.degree. C.
However, an extension of these results on an industrial scale presents difficult problems because, although it is easy to remove it by distillation, at temperatures at which hydrolysis is carried out hydrochloric acid gives rise to acid vapour emissions which make it necessary to operate in an enclosed vessel and to carry out the hydrolysis of proteins in complete batches.
Thus, the low apparent density of some sources of these proteins, such as hog bristles which have an apparent density of 0.2, does not enable a large volume of these proteins to be charged into the hydrolysis reactor without excessively increasing the volume of the reactor.
Additionally, hydrochloric acid is extremely corrosive and makes it necessary to use glass-lined reactors which are particularly expensive.
The use of sulphuric acid instead of hydrochloric acid for the hydrolysis of proteins has also been proposed, especially in the patent U.S.-A-2,657,232.
However, the use of concentrated sulphuric acid does not enable a high yield of amino acids to be obtained, nor does it give a satisfactory hydrolysis, because of the degradation of some of them.
The process according to the present invention makes it possible to overcome these disadvantages, using particular conditions of hydrolysis by sulphuric acid, of which the first acidity with a pKA of -7.5 alone is sufficiently strong to cause the opening ot the peptide linkages.
The use of sulphuric acid for the hydrolysis of proteins is surprising because its second acidity is not used in the hydrolysis reaction and, a priori, it is likely to be detrimental to the stability of the amino acids as they are being formed.
Thus, it is all the more important that this acid is to be used, within the scope of the process according to the present invention, at a concentration which must be maintained throughout the period of the hydrolysis reaction at a minimum of 12N so that the dissolution of the proteins may take place and so that the hydrolysis takes place with a good yield.
It should be noted that this minimum concentration of this diacid is twice that used for hydrochloric acid.
The use of these conditions of hydrolysis with sulphuric acid according to the present invention has important consequences from an economic point of view as well as from a practical point of view.
First of all, hydrolysis in a sulphuric acid medium may be carried out in tanks containing a simple protective lining, which is a much less expensive alternative than the glass linings which are indispensable if the hydrolysis is to be carried out in a hydrochloric acid medium.
Secondly, the boiling point of a mixture of sulphuric acid with the proteins to be hydrolysed during the dissolution being only 120.degree. C., the hydrolysis may easily be carried out at the minimum temperature of 100.degree. C. which is required to obtain a good yield, without the emission of acid vapours, unlike in the case of hydrochloric acid.
Finally and most importantly, as the hydrolysis reaction with sulphuric acid may be carried out under conditions of exposure to air, it will be possible to
REFERENCES:
patent: 2457117 (1948-12-01), Bernardi
patent: 2505129 (1950-04-01), Manning
patent: 2533114 (1950-12-01), Hoglan
patent: 2555276 (1951-05-01), Pattes
patent: 2657232 (1953-10-01), Borkenhagen
patent: 3048627 (1962-08-01), Keil
Laboratoires Flork S.A. Zone Industrielle Du Brezet
Reamer James H.
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