E. coli and S. cerevisiae were encapsulated within alginate/cellulose sulphate-CaCl2/poly(methylene-co-guanidine) (SA/CS-CaCl2/PMCG) capsules. Although PMCG inhibited strongly the growth of E coli and S. cerevisiae in free cultivation, PMCG coated capsules had no negative effects on the growth of free E. coli and S. cerevisiae or on the consumption of glucose in the cultivation of S. cerevisiae. If commercial PMCG agent was pre-treated by the method specified in this paper, E. coli and S cerevisiae immobilised in the SA/CS-CaCl2/PMCG capsules grew almost as normally as in free cultivation. Thus, PMCG was shown to be a suitable membrane material for microorganism encapsulation after it was purified under appropriate conditions. (C) 2004 Elsevier Ltd. All rights reserved.