Abstract
Given its variety of properties, including conductivity and slow corrosion, the industrial uses for gold are increasing dramatically. This means that greater amounts of gold are being released into the environment and that a biological approach to recycling gold is of great interest. Lysinibacillus sphaericus, a bacterium capable of metal accumulation inside the cell and adsorption in the external surface, was encapsulated in an alginate matrix to improve the capture of gold from aqueous media. In this study, L. sphaericus CBAM5 proved to have the greatest potential compared to other strains and, following its encapsulation, the efficiency for the removal of the precious metal, at a concentration of 60 ppm, was 100% after three hours of exposure. It was identified that the alginate spheres with bacteria could also be reused. In fact, an efficiency of 60% was retained after three cycles of utilization. Thus, alginate acts as an adequate immobilization matrix for bacteria as a highly effective gold capture mechanism, which also shows great potential as an alternative for biotechnological applications.
Highlights
The use of gold for the development of new technologies based on gold nanoparticles in the pharmaceutical, electronic, and electrical industries is on the increase [1]
Lysinibacillus sphaericus is a gram-positive bacterium isolated from a uranium mining waste pile [9], which has a surface layer (S-layer) protein, a porous lattice that protects it and acts as an ion trap
flame atomic absorption spectroscopy (FAAS) during during aa period period of of 22 hh because because metal previous studies showed that gold adsorption occurs in a brief period of time
Summary
The use of gold for the development of new technologies based on gold nanoparticles in the pharmaceutical, electronic, and electrical industries is on the increase [1]. Metals 2019, 9, 818 found that L. sphaericus is able to accumulate and adsorb Au(III) and that there is evidence for the biosynthesis of gold nanoparticles or colloids [1,15] Given the protection it provides against environmental stress, the immobilization of bacterial cells could improve their tolerance and capacity to remove contaminants [16]. Alginate is an algal polysaccharide commonly used in the food industry [18] and it has been demonstrated that it may provide an efficient means to encapsulate bacteria to capture heavy metals such as Cr(VI) [12] This type of matrix gives protection to the cell [12,13] but it provides a controlled environment for bacterial cells [18] due to its porosity that allows the dissolved contaminants to pass through it, increasing the retention time in the matrix. A comparative study between free and encapsulated L. sphaericus cells was performed and the gold biosorption efficiency was evaluated
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