Biosorption and Bioleaching of Heavy Metals from Electronic Waste Varied with Microbial Genera

Industrialization and technological advancements have led to the exploitation of natural resources and the production of hazardous wastes, including electronic waste (E-waste). The traditional physical and chemical techniques used to combat E-waste accumulation have inherent drawbacks, such as the production of harmful gases and toxic by-products. These limitations may be prudently addressed by employing green biological methods, such as biosorption and bioleaching. Therefore, this study was aimed at evaluating the biosorption and bioleaching potential of seven microbial cultures using E-waste (printed circuit board (PCB)) as a substrate under submerged culture conditions. The cut pieces of PCB were incubated with seven microbial cultures in liquid broth conditions in three replicates. Atomic absorption spectroscopy (AAS) analysis of the culture biomass and culture filtrates was performed to evaluate and screen the better-performing microbial cultures for biosorption and bioleaching potentials. The best four cultures were further evaluated through SEM, energy-dispersive X-ray spectroscopy (EDX), and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) studies to identify the possible culture that can be utilized for the biological decontamination of E-waste. The study revealed the highest and differential ability of Pleurotus florida and Pseudomonas spp. for biosorption and bioleaching of copper and iron. This can be attributed to bio-catalysis by the laccase enzyme. For both P. florida and Pseudomonas spp. on the 20th day of incubation, laccase exhibited higher specific activity (6.98 U/mg and 5.98 U/mg, respectively) than other microbial cultures. The biomass loaded with Cu2+ and Fe2+ ions after biosorption was used for the desorption process for recovery. The test cultures exhibited variable copper recovery efficiencies varying between 10.5 and 18.0%. Protein characterization through SDS-PAGE of four promising microbial cultures exhibited a higher number of bands in E-waste as compared with microbial cultures without E-waste. The surface topography studies of the E-waste substrate showed etching, as well as deposition of vegetative and spore cells on the surfaces of PCB cards. The EDX studies of the E-waste showed decreases in metal element content (% wt/% atom basis) on microbial treatment from the respective initial concentrations present in non-treated samples, which established the bioleaching phenomenon. Therefore, these microbial cultures can be utilized to develop a biological remediation method to manage E-waste.

Determination of Simvastatin by Voltammetry Method at Screen-Printed Electrode Modified by Graphene Oxide Nanosheets and Sodium Dodecyl Sulfate

An accurate, rapid, simple, and novel technique was developed to determine simvastatin (SMV). In this research, a screen-printed electrode (SPE) was deposited with graphene oxide (GO) and sodium dodecyl sulfate (SDS), respectively. For the first time, the handmade modified SPE measured the SMV by differential pulse voltammetry (DPV) with high sensitivity and selectivity. The results of cyclic voltammetry indicated the oxidation irreversible process of SMV. Various parameters (pH, concentration, scan rate, support electrolyte) were performed to optimize the conditions for the determination of SMV. Under the optimum experiment condition of 0.1 M KNO3 as support electrolyte and pH 7.0, the linear range was achieved for SMV concentration from 1.8 to 36.6 µM with a limit of detection (LOD), and a limit of quantitation (LOQ) of 0.06 and 1.8 µM, respectively. The proposed method was successfully utilized to determine SMV in tablets and urine samples with a satisfactory recovery in the range of 96.2 to 103.3%.

Deletion of YLR358C Contributes to Reduce Cell Wall Integrity in Saccharomyces Cerevisiae

The mechanism of fungal cell wall synthesis and assembly is still unclear. Saccharomyces cerevisiae (S. cerevisiae) and pathogenic fungi are conserved in cell wall construction and response to stress signals, and often respond to cell wall stress through activated cell wall integrity (CWI) pathways. Whether the YLR358C open reading frame regulates CWI remains unclear. This study found that the growth of S. cerevisiae with YLR358C knockout was significantly inhibited on the medium containing different concentrations of cell wall interfering agents Calcofluor White (CFW), Congo Red (CR) and sodium dodecyl sulfate (SDS). CFW staining showed that the cell wall chitin was down-regulated, and transmission electron microscopy also observed a decrease in cell wall thickness. Transcriptome sequencing and analysis showed that YLR358C gene may be involved in the regulation of CWI signaling pathway. It was found by qRT-PCR that WSC3, SWI4 and HSP12 were differentially expressed after YLR358C was knocked out. The above results suggest that YLR358C may regulate the integrity of the yeast cell walls and has some potential for application in fermentation.

Preparation, Properties and Application of Gel Materials for Coal Gangue Control

In order to solve the problem of the spontaneous combustion of coal gangue, a coal gangue fire-extinguishing material of gel–foam was developed. The foaming agent was screened by the Waring blender method with varying foam amounts, and the superabsorbent foam stabilizer was synthesized by free radical polymerization. Moreover, the gel–foam was used in a spontaneous combustion of coal gangue mountain field practice. The results showed that when the mass fraction of sodium dodecyl sulfonate and coconut oil amide propyl betaine was 0.6% and 4:6, the foaming amount was as high as 1500 mL. When the mass ratio of chitosan to acrylic acid was 1:6, the neutralization degree was 80%, the cross-linking agent was 0.8%, and the initiator was 0.01%, the water absorption of the synthesized superabsorbent foam stabilizer reached 476 mL/g. The synthesized gel–foam was tested in a spontaneous combustion coal gangue hill in a certain area, and no reburning sign was found within one month.

Tropomyosin micelles are the major white components in the boiled soup of shellfish

Basket clam soup, a popular Asian dish, is prepared by boiling clams in hot water. The soup is generally cloudy and considered more delicious as cloudiness increases. However, the identity of the whitening ingredients and their relationship with taste remain unclear. In this study, we aimed to identify the components that contribute to the white color of the boiled soup. The white component was precipitated with trichloroacetic acid and reacted positively with ninhydrin, indicating the presence of proteins. The proteins were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and an intense band was observed at 33 kDa. Peptide mass fingerprinting of this band using matrix-assisted laser desorption/ionisation-time-of-flight tandem mass spectrometry revealed the protein to be tropomyosin. Basket clam tropomyosin expressed and purified from Escherichia coli turned the extracted solution white, confirming that tropomyosin contributed to the white color of clam soup.

Qualitative and quantitative methods detection of SDS based on polyelectrolyte microcapsules

Sodium dodecyl sulfate (SDS) is the most widely used anionic surfactant. Its frequent use causes environmental pollution and negative effects on living organisms (even at low concentrations ≈ 20 μg/ml). Thus, cheap and fast methods are needed to detect this surfactant in wastewater and surface waters in order to prevent the negative effects of SDS on the environment and human beings. We discovered that sodium dodecyl sulfate is capable of destroying polyelectrolyte microcapsules, which has been demonstrated by the number of sedimented polyelectrolyte microcapsules (PMC) before and after incubation in SDS solution. Therefore, it was proposed to use PMCs to create qualitative and quantitative diagnostic systems for the determination of SDS in solution. The qualitative system is a polyelectrolyte microcapsules containing polyallylamine labeled with a fluorescent dye—FITC. An excess SDS concentration of more than 5 μg/ml in the analyzed medium leads to the destruction of PMC and an increase in the fluorescence intensity of the solution, which is recorded by a fluorometer. The quantitative diagnostic system is based on turbidimetry of the PMC suspension before and after incubation in an anionic surfactant solution. This system has a range of detectable SDS concentrations from 10 to 50 μg/ml, with a standard deviation of no more than 11%.