Researches on the formation of diastase by Aspergillus niger van Tieghem

Before we experiment with the enzymes of fungi, it is imperative that we should know, what hydrogen ion concentration is wanted for the optimal reaction of these enzymes. Aspergillus niger produces the necessary degree of acidity in its own culture solution. This however is not the case with all fungi. It is of the utmost Importance to know, what nutrient base is used in the cultures, from which we obtain the conidia for our experiments. It is always best to take these conidia from cultures on solutions of the same chemical composition as those, on which we intend to grow them. Aspergillus niger produces large quantities of diastase from the beginning of its development until a maximum is reached. Then no more is secreted, but this maximum amount, which is then present, remains constant during the entire lifetime of the fungus. This was found to be the case when cultivated on glucose, starch and maltose. Neither the chemical composition, nor the quantity of these substances seemed to have any influence. If the concentration of the culture solution is higher than 1%, it may disturb the course of enzyme production temporarily, because certain substances are formed, which inhibit the action of the enzyme. These substances disappear during the course of development and the normal maximal quantity of enzyme is eventually produced. The diastase of Aspergillus niger is secreted into the culture solution immediately after it is formed. The diastase may be kept for a long time without loosing its strength. Saccharose has a deleterious influence on the action of diastase. For some reason or other, the normal amount of diastase appears, after all the cane sugar and its split products have disappeared from the culture solution. When Aspergillus niger was grown on 5% glycerine, no diastase production could be proved at all. Aspergillus niger has no lactase, even if it is grown on lactose. There is therefore practically no development of the fungus on this substance. Before 1 close I have pleasure to thank prof.Dr. F.A.F.C. Went, not only for his very valuable help, but also for his kindly allowing me to proceed with his own experiment and for putting at my disposal all the facilities of the Botanical Laboratory in Utrecht. Without this very material help, I should have been unable to carry out this research. I therefore wish to express my heartfelt thanks at this point. Utrecht, Botanical Laboratory 1920—1922. Presented April 1922.