Research Journal of Chemistry and Environment____________________________________Vol. 24 (2) February (2020) Res. J. Chem. Environ. 148 Review Paper: Microbial and plant assisted remediation of Benzo[α]pyrene from soil and aqueous environment Mandal Sanjeeb Kumar 1 , Das Devlina 2 and Das Nilanjana 3 * 1. Department of Biotechnology, Sri Shakthi Institute of Engineering and Technology, Coimbatore, Tamil Nadu, INDIA 2. Department of Biotechnology, PSG College of Technology, Coimbatore, Tamil Nadu, INDIA 3. Bioremediation Laboratory, School of Bio Sciences and Technology, Vellore Institute of Technology, Vellore-632014, Tamil Nadu, INDIA *nilanjanamitra@vit.ac.in Abstract Benzo[α]pyrene (BaP) is one of the most toxic polycyclic aromatic hydrocarbons (PAHs) in the soil- plant system causing potential carcinogenicity and mutagenicity for human health. The knowledge on the behavior of BaP in soil-plant system as well as aqueous environment is needed for minimizing the risk of human exposure and environmental contamination. BaP, high molecular weight PAH with five benzene rings has been specifically classified as a primary pollutant and group 1 human carcinogen. Bioremediation is an eco-friendly and cost-effective method for reclaiming the environment contaminated with BaP by making use of the microorganisms and plants to eradicate the hazardous effects. The present review is focused on the microbe assisted bioremediation and phytoremediation techniques for the removal of BaP from the soil and aqueous environment. The information provided here will help to plan the research in a better way to develop more sustainable system for remediation of BaP from the environment. Keywords: Benzo[α]pyrene (BaP), Bioremediation, Carcinogen, Phytoremediation, Polycyclic aromatic hydrocarbons (PAHs). Introduction Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants which are widespread in the environment 95 . These pollutants are released from combustion processes through transformation of PAHs by abiotic reactions and biological processes 8 . The special attention paid to PAH compounds was largely due to carcinogenic, mutagenic and teratogenic properties 44 . There is evidence that PAH molecules being attached to ultrafine particle surfaces can be bound to the critical targets in DNA molecules. PAH–DNA adducts can increase the risk of lung and skin cancers in human being 58 . Many researchers reported the effects of PAH compounds on animals and humans leading to the development of a variety of disorders affecting all body systems causing the skin cancer and other skin diseases 15,44 . The PAHs with more than four benzene rings are having the most carcinogenic activity 44,106 . The United States Environmental Protection Agency (USEPA) and European Commission have classified 16 PAHs as priority pollutants based on the toxicity 44,104 . Benzo(a)pyrene (BaP) is having five benzene rings and classified as a primary pollutant. Bioremediation has been accepted as the standard strategy for the restoration of PAH contaminated soil as it is more eco-friendly and cost effective process compared to the existing physico-chemical methods, which are often very expensive and ineffective 23 . This method relies on the metabolism of hazardous compounds by microorganisms, leaving non-toxic by-products in the soil and groundwater 76,83 . Biodegradation is considered as an eco- friendly sustainable measure for the bioremediation of PAHs from terrestrial and aquatic environments 16,61 . The powerful microorganisms can play important role for the degradation or cometabolic oxidization of high molecular weight PAHs. Benzo(a)pyrene (BaP) is considered as representative of PAHs. It is a high molecular- weight polycyclic aromatic hydrocarbon which is highly recalcitrant in nature 71 . It is chosen as a model compound for the investigation of metabolic information related to PAH biodegradation 92,97 . The objective of the present review is to provide the updated information on remediation of BaP from environment which are being adopted by plants and microorganisms. Chemistry of PAHs and their properties: Sixteen PAHs (naphthalene, acenaphthylene, acenaphthene, anthracene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, benzo(a)anthracene, benzo(b)fluoranthene, benzo(k) fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene and indeno(1,2,3-c,d)pyrene) are considered of primary environmental concern according to the US EPA 98 . PAHs have two or more single or fused aromatic rings with a pair of carbon atoms shared between the rings in the molecules. According to their arrangements, they are defined as linear, cluster, or angular 86,100 . Types of PAH according to ring arrangement are summarized in table 1. PAHs are neutral, hydrophobic nonpolar molecules. Physical and chemical characteristics such as hydrophobicity, vapour pressure and solubility in water vary with molecular weight. These characteristics cause differences in redox potential, solubility, volatility, toxicity and environmental/biological degradation resistance 35 .