# Microbial-Based Biotechnology: Production and Evaluation of Selenium-Tellurium Nanoalloys
## 4 Discussion  
The main aim of our study is to produce a nanoalloy of Se and Te via the biological (microbial) method using bacterial species of _L. casei_ NCAIM B 1147. This study opened several questions for our upcoming research on the production and application of Se and Te nanoalloys in medicine and other fields. The main questions that need to be answered are: Can the studied bacteria differentiate between nano-Se and/or nano-Te in their metabolism? To what extent are the studied bacteria tolerant to higher concentrations of Se and/or Te in bulk and in nanoform? The monoclinic Se-NPs were red in color and had a glass transition temperature (Tg) of 31 \({}^{\circ}\)C [36]. Te-NPs are black in color, have a Tg of 37 \({}^{\circ}\)C [37], and can precipitate as an amorphous structure from solution at room temperature, exhibiting elemental Se and Te. The characteristic red and black colors of the solution were attributed to the surface plasmon vibrations and excitation of Se-NPs and Te-NPs [35]. The red color was mainly observed in samples with low concentrations of tellurite and high concentrations of selenite. The opposite phenomenon was observed for black samples. Se-NPs and Te-NPs with diameters of 221.1 nm and 76.1 nm were observed by [PERSON] et al. [34]. Two types of morphology were discussed by [PERSON] et al. [38]. The size of the articular particles ranges from 50 to 600 nm, and the diameter of the sphere ranges from 70 to 300 nm, which correlates with this study. We hypothesized that bacteria cannot distinguish between selenite and tellurite. Therefore, the concentration of SeTe-NAs remains the same as the Se/(Se + Te) molar ratio present in the initial medium. Bacteria may produce proton anti-transporters or reductases. Selenite and tellurite ions may react with these components to form nuclei of Se\({}^{0}\) and Te\({}^{0}\). Subsequently, Se-NPs, Te-NPs, and SeTe-NAs are grown more significantly from these nuclei. Further conversion and aggregation of Se and Te atoms to Se and Te nuclei of selenite and tellurite ions involves an Ostwald ripening mechanism, in which small NPs form nuclei early in the growth stage. It acts as a formative seed and further grows through the maturation process [39]. Tellurium has a much stronger tendency to crystallize in the trigonal phase than selenium [40]. Te nanocrystals formed at the beginning of the synthesis can serve as heterogeneous seeds for the growth of Se and Te formed in the next step. Se and Te can form solids in solution and are isomorphic to each other. In random copolymers, Se and Te atoms are randomly arranged and distributed along the helical chain. The conversion of tellurite to Te\({}^{0}\) and selenite to Se\({}^{0}\) depends on many factors, including the concentration of other ions other than oxyanions, pH, temperature, bacterial growth rate, and the nature of the medium. Previously, Se-NPs and Te-NPs have been shown to prevent biofilm and planktonic growth of _S. aureus_ ATCC 25923, _P. aeruginosa_ PAO1, and  
Figure 5: Se and Te molar ratio correlation between the samples (_p_ < 0.0001). E. coli_JM109. They remove biofilms that have already formed and inhibit the formation of new biofilms. Compared to inorganic selenite, Se-NPs showed higher antimicrobial activity [34]. Se-NPs and Te-NPs obtained from _Ochroductrum_ sp. MPV1 and _Stentrophomonas maltophilia_ Se1 Te02 can induce ROS formation and inhibit microbial growth. Te has the advantage of high optical absorption due to its chiral chain structure. It can be used for photodynamic therapy (PDT) and photothermal therapy (PTT) under single light source excitation. Modification of Te nanomaterials improves their biocompatibility, reduces toxicity, and confirms their therapeutic efficacy in biomedical applications [41]. Similarly, CdTe nanocrystals were obtained when _E. coli_ cells were added to Na\({}_{2}\)TeO\({}_{3}\) and CdCl\({}_{2}\) in a reducing environment. It has photoluminescence corresponding to its size with incubation time.