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. 2020 Feb 26;10(3):408.
doi: 10.3390/nano10030408.

Effective Gold Biosorption by Electrospun and Electrosprayed Bio-composites with Immobilized Lysinibacillus sphaericus CBAM5

Carolina Páez-Vélez  1 , J L Castro-Mayorga  2 , Jenny Dussán  1
Affiliations

Effective Gold Biosorption by Electrospun and Electrosprayed Bio-composites with Immobilized Lysinibacillus sphaericus CBAM5

Carolina Páez-Vélez et al. Nanomaterials (Basel). .

Abstract

Electro-hydrodynamic processing, comprising electrospinning and electrospraying techniques, is a novel technology used in the production of nano- and sub-micro-scale materials with specific properties suitable for environmental remediation processes. Polycaprolactone (PCL) micro-fibrous mats and alginate microcapsules were produced using electrospinning and electrospraying techniques respectively, and Lysinibacillus sphaericus CBAM5, a bacterium capable of metal removal by adsorption and accumulation inside the cell, was immobilized in these matrices. The polymeric structure was able to protect and maintain cell viability and the bio-composite materials were used to capture gold from synthetic water samples. The micro-fibrous membranes with immobilized bacteria were able to remove 93% of the gold after 120 h of inclusion in the aqueous medium. Using a filtration system, an efficiency of 64% was obtained for the removal of the precious metal after 10 cycles of filtration (2 h of exposure to the gold solution). In contrast, the microencapsulated L. sphaericus CBAM5 captured 64% of the gold after 4 h of the assay. Thus, both micro-structured matrices were suitable for the immobilization and protection of L. sphaericus CBAM5 and they showed high efficiencies of gold biosorption. Hence, these bio-composite materials could be used to concentrate gold from industrial wastewaters.

Keywords: Alginate; Gold; Lysinibacillus sphaericus CBAM5; Polycaprolactone; electrospinning; electrospraying.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Representation of the electrohydrodynamic processing used to obtain (a) micro-fibrous mats of Polycaprolactone (PCL) and (b) microcapsules of alginate with L. sphaericus CBAM5.
Figure 2
Figure 2
(a) Scanning electron microscopy (SEM) micrograph of a PCL membrane freshly synthesized (average diameter is 3.5 ± 1.1 µm). (b) SEM micrograph of a PCL membrane with immobilized bacteria (average diameter is 4.72 ± 1.64 µm).
Figure 3
Figure 3
(a) Optical microscopy of the alginate microcapsules with L. sphaericus CBAM5 (average diameter is 0.73 ± 0.06 mm). (b) Optical microscopy of the dripped alginate capsules with L. sphaericus CBAM5 (average diameter is 2.81 ± 0.35 mm) [17].
Figure 4
Figure 4
Gold (10 ppm) biosorption assays with L. sphaericus CBAM5 immobilized in PCL fibrous mats (Fiber + CBAM5) and the fiber without cells (Control) by inclusion in synthetic water and using a filtration system.
Figure 5
Figure 5
SEM micrographs of L. sphaericus CBAM5 cells (a) attached to a PCL microfiber seen with retro-dispersed electrons. (b) EDS analysis of image (a) showing the presence of Au in the cells.
Figure 6
Figure 6
Gold Biosorption assay with L. sphaericus CBAM5 encapsulated in microcapsules of alginate (Electrosprayed CBAM5) and with microcapsules free of bacteria (Electrosprayed Control) for 4 h. Points at 2 and 4 h denoted by a different letter differ significantly at p < 0.05 according to a Student’s t-test analysis.
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