Comparison of phytase production in 20-L batch fermentation The industrial production of recombinant enzyme in batch mode has been mostly applied due to low operation costs and constant productivity. As discussed earlier, the mutant phytase expressed in recombinant E. coli is affected by temperature, carbon supplement and accumulation of acetic acid. The optimal conditions from preliminary results in shake flask culture were consequently undertaken for one-stage and twostage batch operations in 20-L bioreactor. The formation of acetic acid was monitored. Two-stage batch strategy was employed in order to decrease acetate accumulation during the growth phase and increase the overall yield. The profiles of fermentation are
shown in Figs. 4 and 5. The characteristics of fermentation performance in one-stage and two-stage are summarised in Table 2.