Microbiome-mediated nano-bioremediation of heavy metals: a prospective approach of soil metal detoxification

Heavy metal pollution has increased alarmingly due largely to industrialization, intensive agricultural practices and other anthropogenic activities. Soil heavy metal contamination is the serious threat to the food security worldwide. Due to non-degradative nature, metals persist for a longer period of time in the environment, can be toxic to human health and environments. Acknowledging the toxicity threat, various physical, chemical and biological detoxification strategies such as soil stabilization, soil excavation, soil washing, thermal desorption, chemical extraction and phytoremediation, have been employed in laboratory and under field conditions to treat metal contamination. Such techniques have not completely been successful due to cost, technical complexity, generation of secondary pollutants and conflicting results. Nanotechnology, a rapidly evolving field, has recently been used to remediate hazardous metals. Nanoparticles due to their unique chemical and physical properties are considered important in toxicity alleviation from contaminated environment. The integrated nanoparticles-bioremediation strategies called nano-bioremediation is other promising option that stimulate microbiome functions to remove harmful contaminants from the polluted area. The reported metal removal efficiency of nanobioremediation varies between 12% with biogenic palladium nanoparticle prepared from Spirulina platensis to 100% with iron oxide nanoparticle of Geobacter sulforeducens for palladium and chromium, respectively. This review provides the recent information available in literature about the role of nanotechnology in the metal amelioration from contaminated soils. Understanding the mechanistic interactions between soil microbiome, nanoparticles and contaminants is of paramount importance to explore the microbes-based nanoremediation strategies in the inexpensive abatement of metal enriched environment vis-à-vis crop optimization in contaminated fields.