The effect of heavy metals and temperature on microbial growth and lag

A mathematical model to simulate microbial growth and lag time is proposed in the present
work in accordance with Sengor et al. (2009). The model is verified experimentally for a mixed
microbial culture growing at metal free and at Cr(III) or Cr(VI) contaminated environments.
The model is further verified using a monoculture of Pseudomonas sp. growing at metal free
and Zn(II) contaminated environment. The effect of temperature on microbial growth and lag
is also simulated by the model. The simulation results show for the mixed culture that growth
rate decrease with parallel increase in lag time, with the rise of either Cr(III) or Cr(VI)
concentration. For Pseudomonas sp., the simulation indicated that there is almost nil lag time
for growth at 35 ºC, while approximately 10 h lag time is calculated for growth at ambient
temperature (20 ºC). The lag time increases by approximately 6 more hours when 0.01 mM
Zn(II) is added in the growth medium (at ambient temperature). The increase of lag time with
temperature reduction is explained by the fact that the biochemical reactions are slowed down
at lower temperatures. A good correlation between model predictions and simulation results is
observed.