Influence of trace elements on enzyme production: protopectinase expression by a Geotrichum klebahnii strain

With the aim of increasing productivity of a protopectinase-SE process by using a Geotrichum klebahnii strain, studies were carried out with a urea-defined medium to investigate the effect of six trace elements, namely Fe, Zn, Mn, Co, Cu and Mo, on enzyme production. A dramatic beneficial effect was observed when the original concentration of the six trace elements, previously reported, was reduced up to 1:85. In addition, it was proved that Zn and Fe were essential elements required. The enzyme activity value attained with the urea-defined medium containing Zn and Fe at 25.45 and 93.50×10−2 μM, respectively, doubled the value observed with a diluted reference medium containing the six elements. The enzyme activity achieved represents an increase of 18-fold in comparison with the previously reported urea medium.