BACKGROUND: Lactobacillus reuteri NRRL B-14171 was immobilized in spherical calcium alginate beads to study reuterin production. RESULTS: In relation to free cells (82 mmol L-1), the immobilized cells showed a sharp increase in reaction rate and achieved similar conversions with a reduction in the required biomass. Tests for mass transfer limitations on the reaction rate indicated that neither intraparticle nor external constraints were present. Effectiveness factors near 1 were estimated. CONCLUSION: Immobilization induced increased production of reuterin in Lactobacillus reuteri and is a feasible option for increasing process productivity. (C) 2008 Society of Chemical Industry