Optimum pH 6 was identified for maximum yield of yeast biomass and Zrt1 and Fet4 expression level
Based on 24-hour intervals, the group in which maximum growth rate, absorbed zinc, and expression level of Zrt1 and Fet4 in yeast cells had been observed (the group under conditions of 24 h incubation and 25 µg/ml of zinc concentration), was selected; then to identify the optimum pH for this group, proper for maximum zinc absorption, cultivation and zinc treatment was repeated at pH 3, 4, 5 and 6. The maximum growth rate as well as total accumulation of zinc in yeast cells was observed at pH 6; suggesting the optimum pH for 24 h incubation and 25 µg/ml of zinc concentration for maximum yield of yeast biomass (table 2). Also, the expression level of Zrt1 and Fet4 in zinc absorbed yeasts in these different pH values (pH 3-6) was evaluated. The maximum level of Fet4 expression was observed in pH 4, while the equal increment of Zrt1 and Fet4 expression was observed in pH 6 (figure 4).
Table 2. Effect of pH on yield of yeast biomass