Expression of Escherichia coli AppA2 phytase in four yeast systems

To develop an effective fermentation system for producing Escherichia coli phytase AppA2, we expressed the enzyme in three inducible yeast systems: Saccharomyces cerevisiae ( pYES2), Schizosaccharomyces pombe ( pDS472a), and Pichia pastoris ( pPICZ alpha A), and one constitutive system: P. pastoris ( pGAPZ alpha A). All four systems produced an extracellular functional AppA2 phytase with apparent molecular masses ranging from 51.5 to 56 kDa. During 8-day batch fermentation in shaking. asks, the inducible Pichia system produced the highest activity (272 units ml(-1) medium), whereas the Schizo. pombe system produced the lowest activity (2.8 units ml(-1)). The AppA2 phytase expressed in Schizo. pombe had 60-75% lower K-m for sodium phytate and 28% higher heat-stability at 65 degrees C than that expressed in other three systems. However, all four recombinant AppA2 phytases had pH optimum at 3.5 and temperature optimum at 55 degrees C and similar e. cacy in hydrolyzing phytate - phosphate from soybean meal.