Examinando por Autor "Pereira-Reyes, Reinaldo"

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Optimization of the biosynthesis of silver nanoparticles using bacterial extracts and their antimicrobial potential
(Elsevier (Países Bajos), 2023) Solís-Sandí, Iván; Cordero-Fuentes, Sara; Pereira-Reyes, Reinaldo; Jose-Roberto, Vega-Baudrit; Batista-Menezes, Diego; Montes de Oca-Vásquez, Gabriela
Abstract. In the present study, silver nanoparticles (AgNPs) were biosynthesized using the supernatant and the intracellular extract of Cupriavidus necator, Bacillus megaterium, and Bacillus subtilis. The characterization of the AgNPs was carried out using UV–Vis spectroscopy, FTIR, DLS and TEM. Resazurin microtiter-plate assay was used to determine the antimicrobial action of AgNPs against Escherichia coli. UV–Visible spectra showed peaks between 414 and 460 nm. TEM analysis revealed that the synthesized AgNPs showed mostly spherical shapes. DLS results determined sizes from 20.8 to 118.4 nm. The highest antimicrobial activity was obtained with the AgNPs synthesized with supernatant rather than those using the intracellular extract. Therefore, it was determined that the bacterial species, temperature, pH, and type of extract (supernatant or intracellular) influence the biosynthesis. This synthesis thus offers a simple, environmentally friendly, and low-cost method for the production of AgNPs, which can be used as antibacterial agents.
Production of Polyhydroxybutyrate (PHB) by Bacillus megaterium DSM 32 from Residual Glycerol of the Bioenergy Industry
(Tech Science Press (Estados Unidos), 2017) Alvarado-Cordero, Enzo; Montes de Oca-Vásquez, Gabriela; Pereira-Reyes, Reinaldo; Jose-Roberto, Vega-Baudrit; ESQUIVEL, MARIANELLY
Abstract. Biodegradable polymers from renewable resources are generating growing interest in the plastic industry because they have properties similar to synthetic polymers. Polyhydroxyalkanoates, mainly polyhydroxybutyrate (PHB), have mechanical and physicochemical properties very similar to their synthetic counterparts. This work explores the use of residual glycerol from the bioenergy industry for the production of PHB by Bacillus megaterium DSM 32. The glycerol works as a source of carbon and energy. Raw glycerol was purified with sulfuric acid in order to neutralize saponified fatty acids. The purification process generated three different phases. One of the phases was the glycerol-rich layer; this layer was filtered and concentrated by vacuum distillation process. The purity of the glycerol was determined by thermogravimetric analysis (TGA). Additionally, the physicochemical properties, like viscosity, pH, ash content and density, were measured. The experiments were conducted in shake flasks at 30°C and 120 rpm. Different glycerol concentrations (20, 30, 40 g/L) were used to evaluate the influence of the initial concentration of glycerol on the biomass accumulation and biopolymer production. The purified glycerol obtained had a high purity (~ 89.5–92.13%); this material does not contain fatty acids, although it contains ~3.7% salts. The final PHB concentration obtained was 0.054 mg/mL.