Background Multi-walled carbon nanotubes (MWCNTs) are nanoparticles with countless applications. MWCNTs are typically of synthetic origin. However, recently, the formation of MWCNTs in nature after forest fires has been documented. Previous reports have demonstrated the positive effects of synthetic MWCNTs on the germination and development of species of agronomic interest; nevertheless, there is practically no information on how synthetic or natural MWCNTs affect forest plant development. In this report, based on insights from dose-response assays, we elucidate the comparative effects of synthetic MWCNTs, amorphous carbon, and natural MWCNTs obtained after a forest fire on Eysenhardtia polystachya plant. Methods E. polystachya seeds were sown in peat moss-agrolite substrate and conserved in a shade house. Germination was recorded daily up to 17 days after sowing, and plant development (manifested in shoot and root length, stem diameter, foliar area, and root architecture parameters) was recorded 60 days after sowing. Results The treatments with natural MWCNTs accelerated the emergence and improved the germination of this plant, thus while untreated seeds achieve 100% of germination within 16th day, seeds supplemented with natural MWCNTs at doses of 20 µg/mL achieve the above percentage within the 4th day. Natural MWCNTs also promoted fresh and dry biomass in all applied treatments, specially at doses of 40 µg/mL where natural MWCNTs significantly promoted leaf number, root growth, and the dry and fresh weights of shoots and roots of seedlings. Seeds supplemented with doses between 20 and 40 µg/mL of amorphous carbon achieving 100% of germination within the 6th day; however, seeds supplemented either with doses of 60 µg/mL of the above carbon or with synthetic MWCNTs at all the tested concentrations could achieve at most 80 % and 70% of germination respectively within the 17 days. Finally, neither treatments added with amorphous carbon nor those added with synthetic MWCNTs, showed significant increases in the fresh and dry biomass of the tested plant. Likewise, the survival of seedlings was reduced between 10 and 20 % with 40 and 60 µg/mL of amorphous carbon, and with synthetic MWCNTs in all the doses applied was reduced at 30% of survival plants. Conclusions These findings indicate that MWCNTs produced by wildfire act as plant growth promoters, contributing to the germination and development of adapted to fire-prone conditions species such as E. polystachya.

La contaminación de suelo con aceite residual automotriz (ARA) disminuye su productividad. Una alternativa para su eliminación es la bioestimulación (BS) con un abono animal y posterior fitorremediación (FR) con una leguminosa potenciada con bacterias promotoras de crecimiento vegetal (BPCV), para reducirlo a nivel inferior al límite máximo permisible de 4400 ppm de acuerdo con la NOM-138-SEMARNAT/ SSA1-2012 (NOM-138). Los objetivos de este trabajo fueron: i) bioestimulación de un suelo contaminado con 10000 ppm de ARA con lombricomposta y ii) ulterior Fitorremediación con Cicer arietinum y Bacillus cereus /Rhizobium etli. En la BS del suelo la variable respuesta fue la concentración del ARA, mientras en la FR la fenología y biomasa de C. arietinum y la concentración del ARA remanente. Los resultados mostraron que en suelo la BS con lombricomposta al 3% en 3 meses el ARA se redujo a 1370 ppm. En tanto que la FR con C. arietinum y R. etli, redujo el ARA hasta 30 ppm ambos valores inferiores al máximo permitido por la NOM-138. Lo anterior apoya que en suelo contaminado con ARA, la mejor opción de biorrestauración, es la estrategia integral BS y FR potenciada con géneros de BPCV. © 2016. Journal of the Selva Andina Research Society. Bolivia. Todos los derechos reservados. Palabras clave:ARA, mineral, fitodegradación, BPCV, mineralización. Abstract J. Selva Andina Res. Soc.2016; 7(2):66-74.In Soil pollution by waste motor oil (WMO) is reducing its productivity. An alternative for removing WMO from soil is by biostimulation (BIS) applying animal manure and then phytoremediation (PR) by legume improving with plant growth promoting bacteria (PGPB) to reduce WMO concentration at level below 4400 ppm limit permit for the NOM-138-SEMARNAT/SSA1-2012 (NOM-138). The aims of this research were: i) to analyze soil biostimulation polluted by 10000 ppm of WMO applying vermicompost, then subsequent soil phytoremediation with Cicer arietinum inoculated by Bacillus cereus and/or Rhizobium etli. In soil after applying BS by VC was measured WMO soil concentration and ii) for PR was regarded phenology and biomass of C. arietinum and WMO concentration remaining at the end of this step. The results showed that soil biostimulated by VC, WMO was reduced at 1370 ppm, subsequent PR sowing C. arietinum with R. etli, WMR was reduced at 30 ppm concentration both values below to maximum value accepted by NOM-138. Those data indicate that in soil polluted by Historial del artículo.

Multi-walled carbon nanotubes (MWCNTs) are of multidisciplinary scientific interest due to their exceptional physicochemical properties and a broad range of applications. However, they are considered potentially toxic nanoparticles when they accumulate in the environment. Given their ability to oxidize resistant polymers, mycorremediation with lignocellulolytic fungi are suggested as biological alternatives to the mineralization of MWCNTs. Hence, this study involves the ability of two fungi specie to MWCNTs biotransformation by laccase and peroxidases induction and evaluation in vivo of its toxicity using Caenorhabditis elegans worms as a model. Results showed that the fungi Penicillium chrysogenum and Pleurotus ostreatus were capable to grow on media with MWCNTs supplemented with glucose or lignin. Activities of lignin-peroxidase, manganese-peroxidase, and laccase in cultures of both fungi were induced by MWCNTs. Raman, FTIR spectroscopy, HR-TEM, and TGA analyses of the residue from the cultures of both fungi revealed structural modifications on the surface of MWCNTs and its amount diminished, correlating the MWCNTs structural modifications with the laccase-peroxidase activities in the fungal cultures. Results indicate that the degree of toxicity of MWCNTs on the C. elegans model was enhanced by the structure modification associated with the fungal ligninolytic activity. The toxic effect of MWCNTs on the in vivo model of worms reveals the increment of reactive oxygen species as a mechanism of toxicity. Findings indicate that the MWCNTs can be subject in nature to biotransformation processes such as the fungal metabolism, which contribute to modify their toxicity properties on susceptible organisms and contributing to environmental elimination.

Soils contaminated by waste motor oil (WMO) affect their fertility, so it is necessary to recover them by means of an efficient and safe bioremediation technique for agricultural production. The objectives were: (a) to biostimulate the soil impacted by WMO by applying crude fungal extract (CFE) and Cicer arietinum as a green manure (GM), and (b) phytoremediation using Sorghum vulgare with Rhizophagus irregularis and/or Rhizobium etli to reduce the WMO below the maximum value according to NOM-138 SEMARNAT/SS or the naturally detected one. Soil impacted by WMO was biostimulated with CFE and GM and then phytoremediated by S. vulgare with R. irregularis and R. etli. The initial and final concentrations of WMO were analyzed. The phenology of S. vulgare and colonization of S. vulgaris roots by R. irregularis were measured. The results were statistically analyzed by ANOVA/Tukey’s HSD test. The WMO in soil that was biostimulated with CFE and GM, after 60 days, was reduced from 34,500 to 2066 ppm, and the mineralization of hydrocarbons from 12 to 27 carbons was detected. Subsequently, phytoremediation with S. vulgare and R. irregularis reduced the WMO to 86.9 ppm after 120 days, which is a concentration that guarantees the restoration of soil fertility for safe agricultural production for human and animal consumption.

Biorrestauración de suelo contaminado con aceite residual automotriz por bioestimulación con lombricomposta y fitorremediación con Sorghum vulgare inoculado con Bacillus cereus y Rhizobium etli Biorestauration of soil polluted by waste motor oil by biostimulation with vermicompost and phytoremediation with Sorghum vulgare inoculated by Bacillus cereus and Rhizobium etli