The Importance of Inoculum Standardization in Nutritional Experiments With Fungi

Parent culture age, method of homogenation, and quantity of inoculum per culture flask were investigated for their influence on variability in yield in studies of the vitamin nutrition of a low-temperature basidiomycete. Age of parent cultures affected yield both in complete media and in basic (vitamin-free) media, in the latter presumably because of vitamin carry-over. Saline used as a suspending medium for homogenate preparation was found to be inhibitory when compared with water; the length of time of homogenizing, over the range tested, was without significant effect on either the mean yield or the variation between replicates. Variability between replicates was found to be inversely related to the quantity of inoculum per culture flask over a certain range, and yield tended to increase with increasing inoculum up to a limit.The results emphasize the necessity of adopting a standard procedure for the preparation of inoculum if quantitatively reproducible results are to be obtained.