ANTIMICROBIAL EFFECT OF BIOLOGICAL AND CHEMICAL SILVER NANOPARTICLES IN ENVIRONMENTAL SAMPLES

The resistance of bacterial strains to antimicrobial agents and biofilm-associated infections causes considerable economiclosses and worldwide deaths. If this problem continues it is estimated that in 2050, about 10 million human deaths couldoccur per year and the costs would reach 1 trillion USD globally. Most of the studies evaluating the antimicrobial effect ofan antimicrobial agent focus on pure bacterial cultures, even when it is known that microorganisms live in communities interacting with each other, causing a less efficient antimicrobial effect on target compounds. Because of previous data, it is necessary the search for alternative and effective methods that, at the same time, do not generate bacterial resistance;silver nanoparticles (AgNPs) can be an excellent alternative; moreover, the evaluation of these antimicrobial agents onmicrobial communities from environmental samples are needed. In this paper, we synthesized spherical AgNPs by biological and chemical methods with an average diameter of 10.32 and 9.53 nm respectively; we evaluated the antimicrobial effect of both in microbial populations that came from three different environmental samples (computer keyboard, tap water, and pharyngeal exudate). Results showed that both AgNPs are excellent antimicrobial agents obtaining for both inhibition percentages higher than 90%.La resistencia de las cepas bacterianas a los agentes antimicrobianos y las infecciones asociadas a biopelículas provoca pérdidas económicas considerables y muertes en todo el mundo. De  continuar este problema, se estima que en el año2050 podrían ocurrir alrededor de 10 millones de muertes humanas y los costos alcanzarían 1 billón de dólares a nivel mundial. La mayoría de los estudios de evaluación del efecto antimicrobiano se han enfocado en el estudio de cultivos puros, aun cuando se sabe que los microorganismos viven en comunidades que interactúan entre sí, lo anterior ocasionaque el efecto antimicrobiano de los compuestos objetivo sea menos eficiente. Debido a esto, es necesaria la búsqueda de métodos alternativos que sean efectivos y no generen resistencia bacteriana; las nanopartículas de plata (AgNPs) pueden ser una excelente alternativa, así también es muy importante la evaluación de estos agentes antimicrobianos encomunidades microbianas provenientes de muestras ambientales. En este estudio se reporta la síntesis de AgNPs esféricaspor métodos biológicos y químicos con un diámetro promedio de 10,32 y 9,53 nm respectivamente; se evalúa el efecto antimicrobiano de ambos tipos de nanopartículas en la población microbiana proveniente de tres muestras ambientalesdiferentes (teclado de computadora, agua del grifo y un exudado faríngeo). Los resultados mostraron que ambos tipos de AgNPs son excelentes agentes antimicrobianos obteniendo en ambos casos porcentajes de inhibición mayores al 90%

Microbial removal of weathered hydrocarbons by well adapted-bacteria

The effectiveness of bioremediation processes may be limited by the physical and chemical properties of the pollutant, such as availability, recalcitrance, concentration and weathering, among others. The aim of this work was to evaluate the removal of recalcitrant oil fractions (aliphatic-aromatic and asphaltenic fractions) from a weathered soil, by two bacteria adapted to a high concentration of oil hydrocarbons, isolated from a soil with a concentration of 227,000 mg of total petroleum hydrocarbons per kg soil. Kinetics of hydrocarbons removal by Bacillus coagulans and/or Serratia liquefasciens was performed in liquid culture for 168 h; hydrocarbons from soil as sole carbon and energy source (600 mg/l) were added and each of the microorganisms was inoculated for evaluation independently or as a mixed culture. The aromatic fraction was removed by B. coagulans at 330 mg/l; by S. liquefasciens at 130 mg/l; and by both microorganisms at 360 mg/l. The asphaltenic fraction was removed by B. coagulans at 23 mg/l; by S. liquefasciens at 15 mg/l; and by both microorganisms at 34 mg/l. Chromatographic analysis of the aliphatic-aromatic fraction showed the presence of branched aliphatic C6 to C26, polyaromatic substituted compounds of two and three rings, and heteroaromatic compounds of dibenzothiphene type. The compounds that were removed from the aliphatic-aromatic fraction were of all types in the range of C6 to C13.Keywords: Asphaltenes, aliphatic-aromatic fraction, weathered, biodegradationAfrican Journal of Biotechnology Vol. 12(9), pp. 941-94

Actividad antimicrobiana de nanopartículas de plata contra bacterias fitopatógenas

Las nanopartículas de plata (NPAg) representan un prometedor agente antibacteriano para combatir a bacterias fitopatógenas resistentes. Su tamaño nanométrico, les confiere la habilidad para penetrar distintas membranas biológicas como la pared bacteriana, incrementando su efecto bactericida. La presente investigación tuvo como objetivo utilizar  NPAg sintetizadas por vía fúngica, contra bacterias fitopatógenas aisladas de frutos enfermos de diferentes cultivos agrícolas de importancia en la región. Se aislaron en total 21 bacterias fitopatógenas, las cuales fueron identificadas a nivel de género mediante pruebas morfológicas, microscópicas y bioquímicas como: Pseudomonas sp; Serratia sp; Xanthomonas sp; Erwinia sp; y Acinetobacter sp. El efecto de las nanopartículas de plata se evaluó en medio  líquido adicionado con NPAg a diferentes concentraciones, los cuales evidenciaron una inhibición in vitro del crecimiento en un 93% a 99%, utilizando la dilución con una relación 1:5 de NPAg/caldo nutritivo (300 ppm)

New Perspectives on the Application of Chito-Oligosaccharides Derived from Chitin and Chitosan: A Review

The study of chitin and chitosan has stood out for many years due to their potential application in various areas such as the food industry, where they are either used as additives, prebiotics, or bio-conservatives; as to biomedical and pharmaceutical industries, where they function to treat diseases. Besides, in the agriculture field, it is known that they can cause a positive effect on the development of plants and optimize nitrogen fixation. In recent years, attention has been paid to their derivatives, chito-oligosaccharides which, unlike chitin and chitosan, they have different chemical characteristics, like their solubility, a characteristic that facilitates their use, contrary to chitin and chitosan. Moreover, the small size of chito-oligosaccharides can facilitate their entry into the cell. This review covers recent studies on the biological functions of chito-oligosaccharides and their impact on a priority area such as agriculture, where these compounds could be used to substitute the demand for chemical compounds that, until now, have generated serious health issues as well as environmental pollution