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From the experience gained in all of the foregoing studies on the mineral nutrition, the reaction of media, and the general equation of metabolism of Aspergillus niger, and from many experiments not reported in this paper it was concluded that the most suitable medium for conducting the citric acid fermentation with Aspergillus niger should have about the following composi- tion per 1,000 ec. TABLE VII.

Table 4 From the experience gained in all of the foregoing studies on the mineral nutrition, the reaction of media, and the general equation of metabolism of Aspergillus niger, and from many experiments not reported in this paper it was concluded that the most suitable medium for conducting the citric acid fermentation with Aspergillus niger should have about the following composi- tion per 1,000 ec. TABLE VII.

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—eE————E— eee eee complex than was really necessary. This was shown by the later work of Nageli,!! Molisch,” and Benecke.* The combined work of these three investigators showed that after a mold had been supplied with available sources of carbon and nitrogen, four ele- ments only were necessary for growth—potassium, magnesium, phosphorus, and sulfur. No one of these four elements can be replaced by any element of the same chemical group. Molisch thought iron was necessary for the complete development from spore to spore. Benecke tried to settle this question but acknowl- edged that his results were inconclusive. In some cases when no iron salts were added to the media there was no sporification while in other cases there was an abundant development of spores. After observing a very large number of cultures of Aspergillus niger upon media to which no iron salts had been added the writer is of the opinion that iron is not at all necessary for the develop- ment of spores. Indeed in some media iron salts do not even stimulate the development of mycelium or accelerate the rate of metabolism in any way. The only practicable forms in which nitrogen can be offered in inorganic combination are ammonium salts and nitrates. The addition of iron salts to media contain- ing nitrates always accelerates the rate of metabolism and in- creases the weight of mycelium, while if nitrogen be supplied by ammonium salts, of which the ammonium phosphates serve best,
—eE————E— eee eee complex than was really necessary. This was shown by the later work of Nageli,!! Molisch,” and Benecke.* The combined work of these three investigators showed that after a mold had been supplied with available sources of carbon and nitrogen, four ele- ments only were necessary for growth—potassium, magnesium, phosphorus, and sulfur. No one of these four elements can be replaced by any element of the same chemical group. Molisch thought iron was necessary for the complete development from spore to spore. Benecke tried to settle this question but acknowl- edged that his results were inconclusive. In some cases when no iron salts were added to the media there was no sporification while in other cases there was an abundant development of spores. After observing a very large number of cultures of Aspergillus niger upon media to which no iron salts had been added the writer is of the opinion that iron is not at all necessary for the develop- ment of spores. Indeed in some media iron salts do not even stimulate the development of mycelium or accelerate the rate of metabolism in any way. The only practicable forms in which nitrogen can be offered in inorganic combination are ammonium salts and nitrates. The addition of iron salts to media contain- ing nitrates always accelerates the rate of metabolism and in- creases the weight of mycelium, while if nitrogen be supplied by ammonium salts, of which the ammonium phosphates serve best,
Composition of Media in Gm. per 1,000 Cc.
Composition of Media in Gm. per 1,000 Cc.
ve nhibiting Effect of Hydrogen Ion Concentration on Aspergilius niger.
ve nhibiting Effect of Hydrogen Ion Concentration on Aspergilius niger.
In order to study the effect of nitrogen on the acid fermentation yf Aspergillus niger, Culture 142 was grown upon a medium of he following composition:
In order to study the effect of nitrogen on the acid fermentation yf Aspergillus niger, Culture 142 was grown upon a medium of he following composition:
In order to determine the quantity of potassium the medium should contain, four cultures were grown upon 50 cc. of medium of the following composition:
In order to determine the quantity of potassium the medium should contain, four cultures were grown upon 50 cc. of medium of the following composition:
Already many substances of great technical value such as ethyl alcohol, acetic acid, butyric acid, and lactic acid are prepared by biochemical processes. In a recent paper on the chemical activ- ities of yeasts, molds, and bacteria, Ehrlich”? concluded with the prophecy that in time we would have a great chemical fermenta- tion industry in which many substances would be prepared which are now manufactured by expensive synthetic methods. Many such substances are known to occur as metabolic products of microorganisms. The painstaking investigation of all the condi- tions favoring the production of such substances will lay the only sure foundations for the development of a chemical fermentation industry It is the hope of the writer that the work here recorded may prove a definite contribution to this much neglected but promising field of scientific endeavor.
Already many substances of great technical value such as ethyl alcohol, acetic acid, butyric acid, and lactic acid are prepared by biochemical processes. In a recent paper on the chemical activ- ities of yeasts, molds, and bacteria, Ehrlich”? concluded with the prophecy that in time we would have a great chemical fermenta- tion industry in which many substances would be prepared which are now manufactured by expensive synthetic methods. Many such substances are known to occur as metabolic products of microorganisms. The painstaking investigation of all the condi- tions favoring the production of such substances will lay the only sure foundations for the development of a chemical fermentation industry It is the hope of the writer that the work here recorded may prove a definite contribution to this much neglected but promising field of scientific endeavor.
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