Researches on the formation of diastase by Aspergillus Oryzae

1) On buffered nutrient Solutions Aspergillus Oryzae produces diastase in very large quantities: it is secreted into the liquid soon after having been formed and keeps its concentration for an indefinite time. 2) The chemical composition of the food material, twelve kinds of which have been used in the experiments, has no influence whatever on the quantity of diastase. 3) The fungus, on the whole, needs somewhat more time for hydrolysing bioses and polyoses; the above described diastase production occurs all the same, only some weeks later. Especially lactose is hydrolysed with much difficulty. 4) The concentration of the carbonic food material was mostly 0.5 or 1 %; on 5 % Solutions, the quantities of diastase produced, were quite the same. 5) On unbuffered Solutions Aspergillus Oryzae does not grow so well, produces rather much acid and hardly any diastase. Anaerobic respiration occurs, but seems to play no part in this fact. 6) The acid produced is probably oxalic acid; it is possible that it inactivates the enzyme by binding it chemically; when later on the fungus consumes the acid, the diastase becomes free once more. 7) Investigations in vitro seem to confirm the hypothesis, described in 6). 8) The research was carried out with three strains, two of which were very similar; the third behaved very differently all through the experiment. If is argued that this is probably due to the aftereffect of a quite different former medium and that we are not allowed to think of a hereditary variety. 9) Investigations with Aspergillus niger confirmed in the main my former conclusions,. viz. that for this species the formation of diastase corresponds chiefly with the Chemical composition of the food material and not with the degree of acidity. I have once more the great pleasure in thanking professor Dr. G. van Iterson for his kindly allowing me to make this research in his laboratory and for his valuable help in all respects. Also to professor Dr. Joh. \Vesterdijk I wish to express my heartfelt thanks for her extreme kindness in providing me with the strains, with which I carried on this investigation. Finally, I have to thank very cordially my colleague, mr. C. Deel der, Schiedam, for bis friendly readiness to help me once more to correct the translation of this article. Delft, Laboratory for technical botany. May 1927.