Potential of Variovorax paradoxus isolate BFB1_13 for bioremediation of BTEX contaminated sites

Abstract

Here, we report and discuss the applicability of Variovorax paradoxus strain BFB1_13 in the bioremediation of BTEX contaminated sites. Strain BFB1_13 was capable of degrading all the six BTEX-compounds under both aerobic (O2 conc. 8 mg l−1) and micro-aerobic/oxygen-limited (O2 conc. 0.5 mg l−1) conditions using either individual (8 mg‧l−1) or a mixture of compounds (~ 1.3 mg‧l−1 of each BTEX compound). The BTEX biodegradation capability of SBP-encapsulated cultures (SBP—Small Bioreactor Platform) was also assessed. The fastest degradation rate was observed in the case of aerobic benzene biodegradation (8 mg l−1 per 90 h). Complete biodegradation of other BTEX occurred after at least 168 h of incubation, irrespective of the oxygenation and encapsulation. No statistically significant difference was observed between aerobic and microaerobic BTEX biodegradation. Genes involved in BTEX biodegradation were annotated and degradation pathways were predicted based on whole-genome shotgun sequencing and metabolic analysis. We conclude that V. paradoxus strain BFB1_13 could be used for the development of reactive biobarriers for the containment and in situ decontamination of BTEX contaminated groundwater plumes. Our results suggest that V. paradoxus strain BFB1_13—alone or in co-culture with other BTEX degrading bacterial isolates—can be a new and efficient commercial bioremediation agent for BTEX contaminated sites.

Development of a bacterial consortium from Variovorax paradoxus and Pseudomonas veronii isolates applicable in the removal of BTEX

“…S2). As determined previously, isolate BFB1_13 is able to degrade all six BTEX, but mostly benzene, toluene and o -xylene, under both aerobic and oxygen-limited conditions (Benedek et al 2021 ). Besides I.2.A catechol 2, 3-dioxygenase gene ( C23O ) involved in aerobic BTEX biodegradation, it also harbors at least four different I.2.C subfamily affiliating C23O genes, possibly playing a role in the oxygen-limited degradation of simple aromatic hydrocarbons (Kukor and Olsen 1996 ).…”

“…As mentioned earlier, strain BFB1_13 was capable of degrading all six BTEX after only 168 h of incubation (Benedek et al 2021 ). In addition, out of the six BTEX compounds, strain BFHA4_7 degraded only toluene, m - and p -xylene, cometabolically as well, as this will become apparent in later sections of this study.…”

“…According to Satola et al ( 2013 ) V. paradoxus affiliated isolates are capable of degrading a wide variety of recalcitrant organic pollutants such as PAHs, PCBs, dinitrotoluene, and trichloroethylene. Until recently (Benedek et al 2021 ), there was no information regarding the BTEX biodegradation capacity of V. paradoxus pure cultures, although members of the genus Variovorax are often detected at petroleum hydrocarbon contaminated sites where the primary contaminants are simple aromatic hydrocarbons such as BTEX (Hendrickx et al 2006 ; Benedek et al 2016 and 2018 ; Posman et al 2017 ). On the other hand, based on studies dealing with the metabolism and genetics of bacteria degrading simple aromatic hydrocarbons, it is evident that Pseudomonas species are highly involved in the degradation of BTEX (Arenghi et al 2001 ; Hendrickx et al 2005 ; Wang et al 2008 ).…”

“…By using either individual or a mixture of compounds, the BTEX biodegradation potential of V. paradoxus strain BFB1_13 was thoroughly tested previously under aerobic and oxygen-limited conditions and for planktonic and macro-encapsulated cultures (Benedek et al 2018 , 2021 ). According to Benedek et al ( 2021 ), V. paradoxus strain BFB1_13 completely degraded the mixture of BTEX (conc. ~ 1.3 mg l −1 each) within 168 h of incubation under aerobic and oxygen-limited conditions.…”

Microaerobic enrichment of benzene-degrading bacteria and description of Ideonella benzenivorans sp. nov., capable of degrading benzene, toluene and ethylbenzene under microaerobic conditions

“…These C23O genes are mostly associated with Betaproteobacteriales bacteria (Táncsics et al 2010(Táncsics et al , 2012(Táncsics et al , 2013, and some of them are evidently involved in the microaerobic degradation of BTEXs, e.g. in case of the toluene-degrader Zoogloea oleivorans (Táncsics et al 2020) or Variovorax paradoxus, which was capable of degrading all the six BTEX-compounds under both aerobic and microaerobic conditions (Benedek et al 2021). However, still little is known about the role of microorganisms and I.2.C-type C23O genes in microaerobic benzene degradation, since only handful of known cultured bacteria are available yet for the purpose.…”