For the purpose of industrial production and application of isoamylase, the author carried out screening tests, and as a result, a strain of Aerobaeter aerogenes sp. No. 105 was isolated. Isoamylase formation by this strain has been investigated by means of shake culture, batch culture under aeration, feeding culture and continuous culture. As the interesting property of isolated strain, isoamylase activity in the culture filtrate was about 500 units per ml of broth after 100 hours of cultivation using CH_3COONH_4 as a nitrogen source. While, by using （NH_4）_2SO_4 instead of CH_3COONH_4, isoamylase formation and cell growth proceeded simultaneously, but almost all isoamylase activity formed was a cell-bound type after 16-18 hours of cultivation. Its activity was shown to be 120 units per ml of the culture broth （27 units per mg of cell weight）. So, the isolated strain was considered to hold two different isoamylase formation mechanisms representing either way according to the type of the nitrogen sources used. In aerated batch cultivation using 1000 ml jar fermentor, some experiments were performed in order to compare various carbon sources in regard to the quantitative relationship between cell growth and isoamylase formation under the limited condition of cell-bound isoamylase formation. As the results of batch culture, isolated strain showed the suitable property for aerated culture, and cell-bound isoamylase formed quantitatively 25 units per mg of yield cell. However, when cultivation was carried out under the condition of oxygen limiting for cell growth, yield cell per unit consumed carbon source and isoamylase activity per mg of yield cell showed lower numerical values in comparison with another cases. In feeding cultivation based on aerated batch cultivation, the cultivation with a constant level （1.0 ppm） of dissolved oxygen concentration in the broth was carried out to obtain the higher cell conentration in broth. As the results, feeding cultivation in this work was able to produce 12-13 mg per ml of the broth, and isoamylase activity per mg of cell and ml of cultured broth wers 35 units and 420 units respectively. Thus, the feeding culture achieved about 2.5 times of the final yield of isoamylase in the conventional batchwise culture. In order to obtain higher isoamylase activity per unit cell weight, a cell concentration of more than 10（g/l） in the fermentated broth was needed. The presence of an excess carbon source in broth having over 5-6（g/l） of cell concentration caused an oxygen deficiency. Continuous cultivation with control of dissolved oxygen concentration in the broth was used for cell-bound isoamylase formation of isolated strain by regulating the rate of aeration and feed. The cell growth and cell-bound isoamylase formation were stable during continuous cultivation and the carbon source in the feed medium was completely consumed by cells. With respect to cell-bound isoamylase activity, the continuous culture gave the same or more numerical value as in the feeding culture.