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

Abstract

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.