Abstract
The production of extracellular inulinase ( beta -1,2-D-fructan fructanohydrolase, EC 3.2.1.7) was studied in fed-batch cultures of the yeast Kluyveromyces marxianus CBS 6556 at 30 and at 40 degree C. At both temperatures, the final biomass concentration exceeded 100 g/l and more than 2 g enzyme/L of culture supernatant was produced. The biomass yield on O sub(2) at 40 degree C was substantially lower than at 30 degree C. Nevertheless, at 40 degree C a growth rate of 0.20/h could be maintained for a longer period than at 30 degree C. The unexpected higher O sub(2)-transfer rate at 40 degree C is probably due to a lower viscosity of the culture broth. The 40 degree C fermentation took only 33 h as compared to 42 h at 30 degree C. These results indicate that K. marxianus is a promising host for the extracellular production of heterologous proteins under the control of the inulinase promoter.