Modelling the Effect of Copper on the Mo-reduction Rate of the Antarctic Bacterium Pseudomonas sp. strain DRY1

Abstract

Molybdenum reduction by the Antarctic bacterium Pseudomonas sp. strain DRY1 is strongly inhibited by copper. Mo reduction by this bacterium at 10 mM sodium molybdate shows a sigmoidal pattern with lag periods ranging from 7 to 10 h at various concentrations of copper. As the concentration of copper was increased, the overall Mo reduction rate was inhibited with 1.2 mg/L causing the cessation of Mo reduction rate. The modified Gompertz model was utilized to obtain Mo reduction rates at different concentrations of copper. The Mo reduction rates obtained from the modified Gompertz model was then modelled according to the modified Han-Levenspiel, Wang, Liu, modified Andrews and the Amor models. Out of the five models, only Wang, modified Han-Levenspiel and the Liu models were able to fit the curve, whilst the modified Andrews and Amor models were unable to fit the curves. Both the Wang and modified Han-Levenspiel models show acceptable fitting while the Liu model shows poor fitting. Results of the statistical analysis showed that the modified Han-Levenspiel model was the best model based on the lowest values for RMSE and AICc, highest adjusted correlation coefficient (adR2) and values of AF and BF closest to unity. The parameters obtained from the modified Han Levenspiel model, which were Ccrit, max and m which represent critical heavy metal ion concentration (mg/l), maximum reduction rate (nmole Mo blue/h) and empirical constant values were 0.225 (95%, confidence interval from 0.198 to 0.251), 1.200 (95%, confidence interval from 1.180 to 1.220) and 0.443 (95%, confidence interval from 0.261 to 0.626). The modified Han-Levenspiel accurately predicted the critical copper concentration that completely inhibited molybdenum reduction rate in this bacterium.

Modelling the Effect of Copper on the Growth Rate of Enterobacter sp. strain Neni-13 on SDS

“…The parameters obtained from the Han-Levenspiel model (Table 4) were Ccrit 0.209 mg/L (95%, C.I., 0.199 to 0.219), µmax 0.209 h -1 (95% C.I., 0.199 to 0.219) and m 0.472 (95% C.I., 0.383 to 0.561. Because of its ability to forecast the threshold heavy metal concentrations that will fully limit bacterial growth, the Han-Levenspiel model has been widely used to model the inhibitory effect of metals to growth rate of microorganisms on xenobiotics [7,10,15,17].…”

Mathematical Modeling of the Molybdenum Blue Production from Serratia sp. strain DRY5

“…At levels of several parts per million, molybdenum is very poisonous to ruminants, with cows is by far the most impacted [3,4]. A variety of Mo-reducing bacteria have been isolated to date, and several of these bacteria have also been locally identified [5][6][7][8][9][10][11][12]12,13] and several international strains from Egypt, Indonesia, Pakistan and Nigeria [14][15][16][17][18][19][20][21][22][23][24][25] and Antarctica [26][27][28]. In contrast with other heavy metals such as arsenic, selenium and chromium, the presumed low toxicity of molybdenum to humans and other animals has resulted in not many works as a detoxification procedure on molybdenum reduction.…”

“…Mathematical modelling of the Mo-blue production process have been explored previously [20,27,28,34,35]. That being said, the linearization of the Mo-blue output over time profile is used by both of these works to achieve the basic growth rate for further secondary modeling.…”