Bioleaching of silicon in electrolytic manganese residue using single and mixed silicate bacteria

Silver nanoparticles biosynthesis using mixture of Lactobacillus sp. and Bacillus sp. growth and their antibacterial activity

The biosynthesis of nanoparticles offers numerous advantages, including ease of production, cost-effectiveness, and environmental friendliness. In our research, we focused on the bioformation of silver nanoparticles (AgNPs) using a combination of Lactobacillus sp. and Bacillus sp. growth. These AgNPs were then evaluated for their biological activities against multidrug-resistant bacteria. Our study involved the isolation of Bacillus sp. from soil samples and Lactobacillus sp. from raw milk in Dhamar Governorate, Yemen. The synthesized AgNPs were characterized using various techniques such as UV-visible spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The antibacterial properties of the AgNPs were assessed using the modified Kirby Bauer disk diffusion method against multidrug-resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa. Our results demonstrated that the use of a bacterial mixture for biosynthesis led to faster and more effective production of AgNPs compared to using a single bacterium. The UV-visible spectra showed characteristic peaks indicative of silver nanoparticles, while XRD analysis confirmed the crystalline nature of the synthesized particles. FTIR results suggested the presence of capping proteins that contribute to the synthesis and stability of AgNPs. Furthermore, TEM images revealed the size and morphology of the AgNPs, which exhibited spherical shapes with sizes ranging from 4.65 to 22.8 nm. Notably, the antibacterial activity of the AgNPs was found to be more pronounced against Staphylococcus aureus than Pseudomonas aeruginosa, indicating the potential of these nanoparticles as effective antimicrobial agents. Overall, our study highlights the promising antibacterial properties of AgNPs synthesized by a mixture of Lactobacillus sp. and Bacillus sp. growth. Further research is warranted to explore the potential of utilizing different bacterial combinations for enhanced nanoparticle synthesis.

Effects of different silicate minerals on silicon activation by Ochrobactium sp. T-07-B

As a kind of solid waste with a high silicon content, electrolytic manganese residue (EMR) can be utilized as silicon source by plants through bioleaching processes. EMR contains a variety of silicate minerals. In order to determine the source of available silicon in the bioleaching process of EMR, it is necessary to investigate the influence of silicate minerals in EMR on silicon-activating behavior of specific minerals. In this study, Ochrobactium sp. T-07-B was used to conduct bioleaching experiments on five kinds of silicate minerals with different structures (quartz, muscovite, biotite, olivine, and rhodonite); the growth of Ochrobactium sp. T-07-B, their acid- and polysaccharide-producing capacity, and evolution of surface morphology and structure of the silicate minerals in different systems were determined, so as to explore the silicon-activating capacity of Ochrobactium sp. T-07-B and the selectivity toward different minerals in the bioleaching process. Results showed that the effects of Ochrobactium sp. T-07-B for different silicate minerals were obviously different, and the sequence of silicon-activating efficiency from high to low was as follows: muscovite (65.84 mg·L^-1) > biotite (63.84 mg·L^-1) > olivine (55.76 mg·L^-1) > rhodonite (50.98 mg·L^-1) > quartz (23.63 mg·L^-1). Results of this study may be of guiding significance for the future research on the silicon-activating behavior of solid waste.

Reclamation of waste coal gangue activated by Stenotrophomonas maltophilia for mine soil improvement: Solubilizing behavior of bacteria on nutrient elements

The coal gangue has occupied the farmland and caused severe pollution to the surrounding environment, which was discharged with vast amount as a by-product of coal mining and washing. A sustainable and ecological microorganism activation method was proposed to disposal coal gangue as mineral fertilizer. A Stenotrophomonas maltophilia YZ1 bacteria was separated and found to be useful in solubilizing nutrient elements in coal gangue. The contents of available P, available K and available Si in the treated coal gangue reached 278.4 mg/kg, 1305.3 mg/kg and 522.7 mg/kg, respectively. The YZ1 bacteria dissolved the minerals of monetite (CaHPO₄), muscovite and annite by the organic acids, which were the metabolism product of YZ1 bacteria. The solubilizing mechanisms of phosphate minerals included the release of protic and the chelation of organic acid with calcium. The microbial activation method can provide nutrient elements for soil, which may realize the reclamation of coal gangue in a harmless way.

Bioleaching of silicon in electrolytic manganese residue (EMR) by Paenibacillus mucilaginosus: Impact of silicate mineral structures

Electrolytic manganese residue (EMR) is characterized by high silicon content, and thus, is an important silicon source. While considerable research has been conducted on bioleaching EMR for silicon recovery, sufficient information is not available on the impact of specific silicate mineral structures in EMR on silicon bioleaching. In the present study, the mineral composition of EMR was determined firstly, and then the leaching effect of Paenibacillus mucilaginosus on these different silicate minerals were investigated by shake flask experiments. Results showed that the silicon in EMR was mainly composed of quartz, sericite, muscovite, biotite, olivine and rhodonite; Paenibacillus mucilaginosus had a significantly different weathering and decomposition effects on different silicate minerals. Among them, sericite, muscovite and biotite with layered structure had the most obvious silicon leaching effect, followed by rhodonite with island structure, while silicon leaching from olivine with chained structure and quartz with frame structure was much more difficult. One can roughly judge the adaptability of bioleaching of silicon in EMR using Paenibacillus mucilaginosus if the main form of silicate minerals in EMR is determined.