A suspension of 2g Acetobacter aceti IFO3284 in 22 ml water is heated at 37-40≦̸C and mixed with 5 wt.% K-carageenan in 0.8 wt.% saline. The mixture is dropped into 20 wt.% KCl solution to give 70g of immobilized cells. The cells are packed into a column (2x50 Cm). Soybean milk is passed through the column at the rate of 2 ml/min to reduce offensive flavor.