Growth models of Thermus aquaticus and Thermus scotoductus

Members of the genus Thermus family are signifiant producers of secondary metabolites, which are very commonly used in industry. Beside the productivity, it is also important to study the growth curve of each strain. The mathematical models which are commonly used to describe behavior of microbial strains under different physical and chemical conditions can reduce measured data.In this study, the mathematical models which describe only the microbial count were used. For analysis, Verhulst model, von Bertalanffy model and Richards model were chosen.During the cultivation of Thermus aquaticus and Thermus scotoductus strains, optical density (OD) and concentration of microorganisms were measured. The mathematical models were fitted to experimental data. The fitting was made in program MATLAB. The coefficients of models and statistical evaluation of goodness of fit of models were identified from mathematical analyses. Graphs of individual models were plotted with prediction bounds. 95% confidence levels were used to statistical evaluation of goodness of fit of models and prediction bounds.Richards model was evaluted as the most corresponding with experimental data. Similar results were reached using Verhulst model. Von Bertalanffy model was not coresponded with experimental data

Biosorption of Cu, Zn and Pb by thermophilic bacteria – effect of biomass concentration on biosorption capacity

The aim of this work was to study the biosorption capacity of metals copper, lead and zinc by Geobacillus thermodenitrificans and Geobacillus thermocatenulatus. Solution of each metal was mixed with dry biomass and incubated at room temperature. The supernatant was taken and used for complexometric titration. The sorption capacity for Cu2+ was highest when using 0.5 g·l−1 Geobacillus thermodenitrificans (57 ± 4 mg·g−1). The sorption capacity rapidly decreases with increased concentrations. Similarly for Zn2+ ions, the highest sorption capacity was for biomass concentration 0.5 g·l−1 (18 ± 3 mg·g−1) and slowly decreases. For Pb2+ ions, the decrease is almost linear to the biomass concentration 2 g·l−1, i.e. from 117 ± 13 mg·g−1 to 53 ± 3 mg·g−1.The sorption capacity of Cu2+ ions was highest at the lowest biomass concentration of Geobacillus thermocatenulatus (65 ± 3 mg·g−1), then it sharply decreased and at concentration of biomass of 1 g·l−1 did not changed. In the case of Zn2+ ions, we could seen a moderate drop with the increasing concentration with the range of 24 ± 3 to 12.3 ± 0.4 mg·g−1. For Pb2+ ions was the decrease slow, from 119 ± 8 mg·g−1 to 54 ± 4 mg·g−1.Affinity of metals to bacteria was determined in the order Pb2+ > Cu2+ > Zn2+. The results show, that Geobacillus thermocatenulatus has better sorption capabilities than Geobacillus thermodenitrificans