Owing, however, to the varying composition of the dung used, the bate made therefrom possesses varying properties, its bating action is uncertain, its properties are readily affected by atmospheric influences, and the skins treated are liable to putrefaction.
As a substitute for dung bate, it has been proposed, as set forth in the Specification of Patent No. 21,720, A.D. 1895, to use a bate made from a pure culture of bacteria. Such bate, however, does not possess all the essential properties of a dung bate; and although bacterial action is necessary, such action alone is not sufficient, as was pointed out by the present inventor in 1894 in the “Journal of the Society of Chemical Industry.”
The present inventor has now discovered that the bating action of a dung bate is due to the combined action of enzymes or unorganized ferments, and to certain amine compounds in the dung. These compounds consist of amines (i.e. ammonia in which one or more atoms of hydrogen has or have been replaced by alcohol radicles), in combination with lactic, acetic and other organic acids contained in the dung, the acids named being the principal ones.
The present inventor has also discovered that the bating action of the enzymes alone, or the action of the chemical compounds alone, are inefficient, and that the enzymes exert their bating action in the presence of the chemical compounds, while these latter in addition have an independent action.
The object of this invention is the production, according to scientific methods, of a bate having similar properties to those of a dung bate, such properties in the improved bate being defined and definite, but capable of being modified according to the requirements of the skins to be bated and the leather to be produced.
According to this invention, the liquid or bate is made by producing by fermentation an enzyme or enzymes of the same character as the enzymes contained in dog dung or produced from bacteria obtained from dung, and to the liquid thus obtained there is added an organic acid and an alkali.
The inventor has discovered that for an efficient bate a pure culture of bacteria is insufficient, and that no single organism hitherto isolated will give results equal to dung. He has also discovered that the production of these enzymes depends more upon the composition of the nutrient medium in which the bacteria are cultivated than upon the kind of bacteria, although these latter must be capable of producing the required enzymes, the production of which appears to be due to a symbiotic growth of bacteria, at present little understood.
It is desirable that the nutrient medium should be without sugars or starchy matters, and, although the composition of the nutrient medium may be varied, good results can be obtained according to ordinary bacteriological methods by using a medium composed of—
| Gelatin | 50 | parts |
| Potassium or sodium phosphate | 1 | do. |
| Water | 2500 | do. |