Indigo fermentation has been performed by solubilization of water-insoluble indigo by the action of reducing ability of the microbiota. For this realization, preparation of the appropriate microbiota is indispensable. On the other hand, composted leaves of knotweed indigo, sukumo has been used as the raw material that is used as both the indigo source and bacterial inoculum. At the beginning of the fermentation, sukumo is treated by hot wood ash extract. However, the real influence of the high pH and the heat to the involving microbiota has not known yet. Therefore, in order to understand the impact of the environmental factors involving in this treatment to the microbiota, we analysed the changes of the microbiota in the differently prepared fermentation batches.