BIO-PRECIPITATES PRODUCED BY TWO AUTOCHTHONOUS BORON TOLERANT STREPTOMYCES STRAINS

Boron contamination and its risk management in terrestrial and aquatic environmental settings

Boron (B) is released to terrestrial and aquatic environments through both natural and anthropogenic sources. This review describes the current knowledge on B contamination in soil and aquatic environments in relation to its geogenic and anthropogenic sources, biogeochemistry, environmental and human health impacts, remediation approaches, and regulatory practices. The common naturally occurring sources of B include borosilicate minerals, volcanic eruptions, geothermal and groundwater streams, and marine water. Boron is extensively used to manufacture fiberglass, thermal-resistant borosilicate glass and porcelain, cleaning detergents, vitreous enamels, weedicides, fertilizers, and B-based steel for nuclear shields. Anthropogenic sources of B released into the environment include wastewater for irrigation, B fertilizer application, and waste from mining and processing industries. Boron is an essential element for plant nutrition and is taken up mainly as boric acid molecules. Although B deficiency in agricultural soils has been observed, B toxicity can inhibit plant growth in soils under arid and semiarid regions. High B intake by humans can be detrimental to the stomach, liver, kidneys and brain, and eventually results in death. Amelioration of soils and water sources enriched with B can be achieved by immobilization, leaching, adsorption, phytoremediation, reverse osmosis, and nanofiltration. The development of cost-effective technologies for B removal from B-rich irrigation water including electrodialysis and electrocoagulation techniques is likely to help control the predominant anthropogenic input of B to the soil. Future research initiatives for the sustainable remediation of B contamination using advanced technologies in soil and water environments are also recommended.

Biotechnological potential of microorganisms isolated from the salar del hombre muerto, Argentina

Bacterial strains were isolated from soil and aqueous solution samples from the Salar del Hombre Muerto, Argentina. A total of 141 strains were characterized and the tolerance to sodium chloride was evaluated. We performed a screening to search for molecules of biotechnological interest: carotenoids (11%), emulsifiers (95%), and exopolysaccharides (6%), and to assess the production of enzymes, including proteolytic (39%), lipolytic (26%), hemolytic (50%), and catalase activities (99%); 25 bacterial strains were selected for further studies. Some of them produced biofilms, but only Bacillus sp. HA120b showed that ability in all the conditions assayed. Although 21 strains were able to form emulsions, the emulsifying index Kocuria sp. M9 and Bacillus sp. V3a cultures were greater than 50% and, emulsions were more stable when the bacteria grew in higher salt concentrations. Only pigmented Kocuria sp. M9 showed lipolytic activity on olive oil medium and was able to produce biofilms when cultured without and with 4 M of NaCl. Yellow pigments, lipase activity, and biosurfactant production were observed for Micrococcus sp. SX120. Summarizing, we found that the selected bacteria produced highly interesting molecules with diverse industrial applications and, many of them are functional in the presence of high salt concentrations.

Potential of Bioremediation and PGP Traits in Streptomyces as Strategies for Bio-Reclamation of Salt-Affected Soils for Agriculture

Environmental limitations influence food production and distribution, adding up to global problems like world hunger. Conditions caused by climate change require global efforts to be improved, but others like soil degradation demand local management. For many years, saline soils were not a problem; indeed, natural salinity shaped different biomes around the world. However, overall saline soils present adverse conditions for plant growth, which then translate into limitations for agriculture. Shortage on the surface of productive land, either due to depletion of arable land or to soil degradation, represents a threat to the growing worldwide population. Hence, the need to use degraded land leads scientists to think of recovery alternatives. In the case of salt-affected soils (naturally occurring or human-made), which are traditionally washed or amended with calcium salts, bio-reclamation via microbiome presents itself as an innovative and environmentally friendly option. Due to their low pathogenicity, endurance to adverse environmental conditions, and production of a wide variety of secondary metabolic compounds, members of the genus Streptomyces are good candidates for bio-reclamation of salt-affected soils. Thus, plant growth promotion and soil bioremediation strategies combine to overcome biotic and abiotic stressors, providing green management options for agriculture in the near future.