Porous capsules suitable for immobilizing yeast and Escherichia coli were prepared by the phase separation of poly(m-phenylene isophthalamide) solution. The microorganisms were coated with starch or dextrin, which was subsequently extracted after capsule formation but served both to position the microorganisms in the capsule pores and to form spaces around the microorganisms. Fermentation experiments were carried out with capsules immobilizing yeast. Yeasts could be cultivated in the capsules, and effective release of CO(2) produced by the fermentation was observed with capsules prepared using polyethylene glycol because of the porous structure at the capsule surfaces. Notably, yeasts could be cultivated at high density even after 1 year. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 321-326, 2011