Abstract
In this study, we report on the development of a novel bacterial consortium, consisting of Variovorax paradoxus and Pseudomonas veronii isolates, applicable in the biodegradation of all six BTEX compounds (benzene, toluene, ethylbenzene, o-, m- and p-xylene) and the bioremediation of contaminated sites. The co-cultivability of the selected bacterial isolates was determined in nutrient-rich medium, as well as in BTEX amended mineral salts solution using Terminal Restriction Fragment Length Polymorphism (T-RFLP) and CFU determinations. BTEX biodegradation capacity of the two-strain consortium was assessed in mineral salts solution, where a series of BTEX depletions and supplementations occurred, as well as in a real, BTEX polluted environmental sample (contaminated groundwater) in the presence of the autochthonous bacterial community. The obtained results indicated that the developed bacterial consortium is very efficient in BTEX biodegradation. Under laboratory conditions, the acclimatized bacterial consortium completely degraded the BTEX mixture with a concentration as high as 20 mg l−1 in a mineral salt medium within a short span of 6 h. Close to in situ groundwater conditions (incubated at 15 °C under static conditions in the absence of light), groundwater microcosms containing the autochthonous bacterial community inoculated with the developed bacterial consortium showed more efficient toluene, o-, m-and p-xylene biodegradation capacity than microcosms containing solely the native microbial population originally found in the groundwater. In the inoculated microcosms, after 115 h of incubation the concentration (~ 1.7 mg l−1 each) of o-, m- and p-xylene decreased to zero, whereas in the non-inoculated microcosms the concentration of xylene isomers was still 0.2, 0.3 and 0.3 mg l−1, respectively. The allochthonous bioaugmentation of the contaminated groundwater with the obtained inoculant was successful and manifested in a better BTEX degradation rate. Our results suggest that the obtained bacterial consortium can be a new, stable and efficient bioremediation agent applicable in the synergistic elimination of BTEX compounds from contaminated sites.
Highlights
IntroductionAccording to the U.S EPA, BTEX compounds (benzene, toluene, ethylbenzene, o-, m- and p-xylene) are considered as priority pollutants with significant public health concerns
According to the U.S EPA, BTEX compounds are considered as priority pollutants with significant public health concerns
BTEX biodegradation capacity of the two‐strain consortium in mineral salts solution Within the inoculated samples, after 24 h of incubation a significant concentration reduction was observed in toluene, m- and p-xylene, with the concentration of these compounds decreasing to zero
Summary
According to the U.S EPA, BTEX compounds (benzene, toluene, ethylbenzene, o-, m- and p-xylene) are considered as priority pollutants with significant public health concerns. They are included in the list of Hazardous Air Pollutants (rank 78) in the CERCLA List from the 275 substances determined as significant threats to human health (Rahul and Balomajumder, 2013). O-, mand p-xylene may cause neurotoxicity and reproductive dysfunction (Wilbur and Bosch 2004). Despite their detrimental effects on human health, BTEX are one of the most commonly used chemicals in industries such as petroleum, solvent, paint, adhesives, rubber and pesticide (Abumaizar et al 1998; Atlas and Philp 2005; Fayemiwo et al 2017). As a matter of fact, the principal sources of BTEX pollution are the aforementioned industries supplemented with coal and biomass burning or the exhaust emissions in urban environments (Kelley et al 1997; Baltrenas et al 2011; Mitra and Roy 2011; Datta et al 2013; Prestes de Castro et al 2015; Adamović et al 2018; Zhang et al 2020)
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