Action of Koji Extract Upon Some Carbohydrates

The solution which is prepared by digesting koji in water possesses certain active properties which cause it to resemble in general character the aqueous solution of malt, so carefully experimented upon by Messrs. Brown and Heron. It is of interest and importance to compare the action of koji extract upon the principal carbohydrates in order to establish an identity or a difference between the two species of diastase. From the mode of production there is no reason to suppose that they will be found to be identical, and experiments to be hereafter described will prove that, though they agree in some points, they differ in yet others. The carbohydrates which have been subjected to the action of koji extract are cane-sugar, maltose, dextrin, and gelatinized starch.

Brown and Heron have shown that when an aqueous solution of malt is allowed to remain in contact with a solution of cane sugar, a change takes place by which the cane sugar is made to take up water and is thereby converted into invert sugar, a mixture of dextrose and levulose. The diastase of malt is said by them to exert its maximum effect upon sugar at 55°C; its action is considerably weakened at 60°C and almost destroyed at 66°C.

Experiment shows that the extract of koji also possesses the property of causing cane sugar to become inverted, but I am not able to define the limits of its action. The following experiments will suffice to prove this point.

Experiment 1: 1.974 gram of dry cane sugar was dissolved in 25 cc of koji extract, then diluted with water to 100 cc. The amount of rotation was found to be 15.8 divisions, and the calculated number 15.5 divisions.

1.974 grams case sugar dissolved in 100 c.c. gives rotation = 12.1 div.

25 c.c. koji solution diluted to 100 c.c. gives rotation = 3.4

After being allowed to stand for 18 hours at about 10 to 12°C the rotation was found to have diminished to 5 divisions, and the solution contained 1.67 grams of glucose. Deducting 0.36 gram contained in 25 cc of koji solution, the amount, formed from the cane sugar was 1.31 gram, equivalent to 1.2445 gram cane sugar and hence 0.7294 gram of unaltered cane sugar was present. We thus find the calculated number of divisions rotated by the inverted solution to be +5.43 against 5 divisions actually observed.

Unaltered cane sugar (0.7294 grams in 100 c.c.) +4.4 div.

Koji extract (25 c.c.) in 100 c.c. of water) +3.4 div

Invert sugar formed -2.37 div.

Calculated in degrees of arc the specific rotatory power of the can sugar has been reduced from 74° to 10°.

Experiment 2: A solution of case sugar containing 5.41 grams in 100 cc, and giving a rotation in a 200 mm tube of 33.1 divisions, equal to [a] = 74°, was employed. 75 cc of this solution was mixed with 25 cc of a solution of koji which contained in 100 cc 1.46 gram of solid matter, 1.0125 gram of glucose, and which gave in a 200 mm tube an optical rotation of 8 divisions. It may be remarked that from this and other experiments made with the same solution of koji, it was found to be exceptionally weak in its converting power. The observations are as follow, after deducting the optical rotation due to the presence of the koji solution:


Specific rotatory



At starting

24.8 div.


After 1-1/2 hours at 15°C



After 20-1/4 hours at 10-12°



After 3/4 hour more at 40°C



50 cc of this mixture and 25 cc of koji were treated as below. The numbers given are corrected for the koji present:

Optical Specific rotatory rotation power

The experiment was not carried further than this. At low temperature the converting action of this particular extract of koji is very slow, but at higher temperatures, and especially at from 45° to 50°C it is much more rapid. In this respect, therefore, koji extract resembles malt extract.

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