Bioremediation potential of natural polyphenol rich green wastes: A review of current research and recommendations for future directions

'Green waste' (food, agro-industrial and forest residues) is a renowned valuable resource of polyphenols. Natural polyphenols are relatively efficient in the clean-up of environmental pollutants based on their unique traits of chelation, adsorption, reduction, complexation, nutrient cycling, antibacterial effects and plant growth promotion. These significant traits have found emerging applications in the removal of heavy metals, pathogenic bacteria and dyes from contaminated soil and water through existing bioremedial techniques such as biosorption, phytoextraction and coagulation. Increasingly, polyphenol-rich natural extracts harnessed for green nanoparticle synthesis (production of particles between 1 and 100 nm in size using biological entities such as microorganisms or plant biomass) have found promising use as a remedial agent in the detoxification of toxic pollutants. However, current bioremediation approaches do not sufficiently exploit natural polyphenols, which are abundantly available and are nontoxic. This review examines the extent of natural polyphenol availability in green waste, and provides a critical view on the existing remedial options, knowledge gaps and hence scope for future research. It highlights the use of natural polyphenol-rich green wastes as nanofertilizers, bioamendments, biofilters and bacteriostats. Field application strategies such as microbe-assisted phytoremediation, bioaugmention and biostimulation are also emphasized, showing the multifunctional biotechnological potentials offered by natural polyphenols. (C) 2015 Elsevier B.V. All rights reserved.