Viable cells of Kluyveromyces lactis, transformed with the glucoamylase gene from Arxula adeninivorans, were entrapped in beads of Ca-alginate and employed on a lab scale in a fluidised bed reactor, operating as a two-(liquid-solid) or three-(gas-liquid-solid) phases system, to produce glucoamylase. The reactor was fed with a non-selective medium containing lactose as carbon source and filled with beads that were checked for size and measured 0.21 +/- 0.02 cm in diameter. The performance of the three-phase system, in terms of specific glucoamylase productivity, was twice as high (0.017 U mg cell(-1) h(-1)) than that of the two-phase operating system. Further, higher product concentrations in the outlet were achieved, due to the possibility to enhance the average residence time of the substrate. (c) 2006 Elsevier Ltd. All rights reserved.