Mathematical model and specific growth rate of Acidithiobacillus ferrooxidans in a liquid culture under laboratory conditions

Abstract

In the bioleaching of low-grade ores to recover metals such as copper, silver, zinc or uranium, Acidithiobacillus ferrooxidans is widely studied and used. Its biomass can be inoculated on minerals to improve bioleaching; however, it is dependent on the environmental conditions in which it develops. In this sense, determining a mathematical model that represents the whole process of obtaining biomass, as well as its specific growth rate, under certain conditions, is very important, since it can be used to optimize, predict, compare and monitor the bioleaching process. The objective of this research was to establish the mathematical model and the specific growth rate of Acidithiobacillus ferrooxidans in a liquid culture under certain laboratory conditions. The bacteria were consecutively reactivated twice in 9K culture medium and subjected to adaptation in liquid culture with OK medium with arsenopyrite 1 % (w/v) and incubated at 25 °C with aeration. A single treatment was had with two replicates, each using a glass flask bioreactor containing 630 ml of 0K medium, A. ferrooxidans (70 ml) and Arsenopyrite 8 % (w/v) and incubated at 25° C with aeration for 288 hours. Cell microscopic counts were performed every 48 hours. The data obtained were plotted as decimal logarithm of cell concentration versus time to establish the curve of lines and points, which was used to determine the curve and polynomial equation as a mathematical model with the help of Matlab software. Similarly, it was used to determine the maximum point of the logarithmic phase of the growth curve and the specific growth rate. The mathematical model representing the biomass production was a fourth degree polynomial equation with a maximum biomass production of A. ferrooxidans of 1.13 x 108 cells/ml and a specific growth rate of 0.03 h-1.