Effects of pH on the growth rate exhibited of the wild-type and Cd-resistant Dictyosphaerium chlorelloides strains

Abstract

Environmental factors such as pH affect the growth rate, productivity, and the toxicity of metals in microalgae. This research reports the exponential growth of both wild-type (Dc1M wt ) and cadmium-resistant (Dc RCd100 ) strains of Dictyosphaerium chlorelloides under different pH ranges at 1 to 15 days of exposure. The results reveal that Dc RCd100 strain had a maximum growth rate at pH ranges close to neutrality as time increases (pH 8.0, m = 0.93 on 10 th day), besides with limited growth capacity to moderately acidic pH (pH 4.0, m = 0.67 at 1 st day; pH 5.0 m = 0.16, 0.13 at 10 and 15 th days respectively). Whereas, Dc1M wt strain grows with a maximum growth rate at pH 9.0, with an increase at longer exposure time (m = 2.17 on the 15 th day). However, this strain was unable to maintain growth rates at the lowest pH tested at all exposure times. These results suggested that Dc RCd100 shows changes in cell division as well as in the photosynthetic activity to cope with slightly acidic pH ranges, although it was unable to grow in alkaline environments.