Industrialization led to the release of synthetic and toxic compounds. Partial or improper treatment increases environmental pollution. Conventional methods possess more disadvantages, such as increased duration of degradation and release of secondary pollutants. The drawbacks paved the way for the significant bioremediation perspective. The ubiquitous nature of microbes enables it to utilize toxic compounds, which attracted the focus of treatment towards the biological and eco-friendly methods. The recent decade has shown interest in the application of indigenous microbes in the polluted environment. Apart from the microbial application, phytoremediation is an emerging tool for treating soil contaminated with hazardous pollutants. Technological advancement in biotechnology ensures a safe and healthy environment for a better future.
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Rapid urbanization has led to the development of transport facilities and industries, destroying productive land ecosystems (Nawarot et al., 2006). Anthropogenic activities contribute the majority to pollution. The massive concern is soil contamination and emerging it as a “universal sink” (Doran, 1996). The recalcitrant substances resistant to degradation are known as xenobiotic compounds. The term xenobiotic is derived from the Greek word ‘xenos’, which means foreign or strange, and 'bios,' which means life. Chemicals beyond its threshold cause pollution and harm to humanity (Embrandiri et al., 2016). The accumulation of these compounds will be ascending as it passes through various levels of the food chain (Dubey et al., 2014). Pollutants are merely classified as biodegradable, partially degradable, and non-biodegradable compounds based on the degradable nature. The toxicity and concentration of these substances in the environment alter the ecosystem (Mishra et al., 2019). Bharadwaj (2018) has reported bacteria and fungi in converting problematic pollutants into simpler non-toxic forms. Junghare et al. (2019) have reported the role of Syntrophorhabdus aromaticivorans in the anaerobic remediation of isophthalate, a xenobiotic compound. Bioremediation using microbes employs diverse metabolic pathways for generating enzymes (Sharma et al., 2018; Dangi et al., 2019). The current scenario focus on overcoming the time consumption, minimal removal of hazardous toxicants, loss of ecological balance, and off-odours generated in the environment during the conventional treatment methods (Barghava et al. 2019; Dangi et al. 2019; Kumar and Femina Carolin, 2019).
Havugimana et al. (2015) reported on the wide range of organic pollutants such as PolyChlorinated Biphenyls (PCBs), Polybrominated biphenyls, PolyChlorinated DibenzoFurans (PCDFs), Polycyclic Aromatic Hydrocarbons (PAHs), organophosphorus, carbamate insecticides/ pesticides, herbicides, organic fuels and pharmaceuticals, and their metabolites. Pesticides applied to increase the yield have turned out to be a bane disturbing flora and fauna of the natural habitat (Nishimoto, 2019; Tuomisto et al., 2017). The application has created a negative impact in neurological, reproductive, and oncogenic effect on children (Cognitive development) and pregnant women (Fetal death/anomalies) (Ward et al., 2006; Bouchard et al., 2011; Carmichael et al., 2016; Rahbar et al., 2016).
Studies focus on green remediation of soil pollutants using microbes like bacteria, fungi, algae, and plants.Bioremediation has gained a lot of attention for remediating different contaminants, especially for compounds like volatile organic compounds - benzene, toluene, ethylbenzene, xylene (BTEX) compounds, phenolic compounds, PAHs, petroleum hydrocarbons, nitroaromatic compounds, metals, complex (high molecular weight) PAHs, and chlorinated hydrocarbons- (Kumar and Femina Carolin, 2019). Based on the nature of pollutants, various methods for removing xenobiotics are practised, like in-situ and ex-situ bioremediation processes. In-Situ methods are cost-effective and economical compared with Ex-Situ procedures (Azubuike et al., 2016). Studies are focused on contemporary heterogeneous bioremediation approaches to accelerate the degradation rate and enable it to be cost-effective (Cassidy et al., 2015; Garcı´a-Delgado et al., 2015; Martı´nez-Pascual et al. 2015).
The impact of recalcitrant compounds on the environment and living systems are explored in the past and recent decades. The present chapter attempts to review the varied bioremediation and phytoremediation strategies employed from past decades to treat various xenobiotic compounds posing an offensive threat to the ecosystem. It gives an overview of the different sources of xenobiotic pollutants; the hazardous effects generated due to the presence of these recalcitrant compounds, the in-situ and ex-situ micro remediation techniques, the eco-friendly phytoremediation approaches and integrated degradation approaches using plant and microbes.