Heterologous glucoamylase production with immobilised Kluyveromyces lactis cells in a fluidised bed reactor operating as a two-(liquid/solid) or a three-(gas/liquid/solid) phases system

Viable cells of Kluyveromyces lactis, transformed with the glucoamylase gene from Arxula adeninivorans, were entrapped in beads of Caalginate 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 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.