Elucidating the Relative Roles of Ammonia Oxidizing and Heterotrophic Bacteria during the Biotransformation of 17α-Ethinylestradiol and Trimethoprim

Abstract

The biological fate of 17α-ethinylestradiol (EE2; 500 ng/L to 1 mg/L) and trimethoprim (TMP; 1 μg/L to 1 mg/L) was evaluated with flow through reactors containing an ammonia oxidizing bacterial (AOB) culture, two enriched heterotrophic cultures devoid of nitrifier activity, and nitrifying activated sludge (NAS) cultures. AOBs biotransformed EE2 but not TMP, whereas heterotrophs mineralized EE2, biotransformed TMP, and mineralized EE2-derived metabolites generated by AOBs. Kinetic bioassays showed that AOBs biotransformed EE2 five times faster than heterotrophs. The basal expression of heterotrophic dioxygenase enzymes was sufficient to achieve the high degree of transformation observed at EE2 and TMP concentrations ≤ 1 mg/L, and enhanced enzyme expression was not necessary. The importance of AOBs in removing EE2 and TMP was evaluated further by performing NAS experiments at lower feed concentrations (500-1000 ng/L). EE2 removal slowed markedly after AOBs were inhibited, while TMP removal was not affected by AOB inhibition. Two key EE2 metabolites formed by AOB and heterotrophic laboratory-scale chemostats were also found in independent laboratory-scale mixed culture bioreactors; one of these, sulfo-EE2, was largely resistant to further biodegradation. AOBs and heterotrophs may cooperatively enhance the reliability of treatment systems where efficient removal of EE2 is desired.

Elucidating the impact of microbial community biodiversity on pharmaceutical biotransformation during wastewater treatment

“…For example, Khunjar et al . (2011) found that both ammonia oxidizing bacteria (AOB) and heterotrophs were capable of catalysing the hydroxylation of EE2, likely using a monooxygenase enzyme, but AOB perform the process more rapidly than heterotrophs. Thus, understanding ‘who’ is performing the function may be more important than the expression of the relevant functional gene to understand what controls a biotransformation rate.…”

“…Genes catalysing more specific initial transformations were associated with the transformation of individual compounds. For example, the gene encoding for subunit C of the ammonia monooxygenase gene was associated with EE2 biotransformation (Benjamini–Hochberg adjusted P  =   0.025, ρ = 0.69, adjusted for multiple comparisons), as we would expect given our knowledge of the transformation pathway (Khunjar et al ., 2011). In addition, genes encoding amidase enzymes were associated with atenolol transformation (Helbling et al ., 2010) (Benjamini–Hochberg adjusted P  <   0.03, ρ > 0.78).…”

Trace organic contaminants in biosolids: Impact of conventional wastewater and sludge processing technologies and emerging alternatives

“…Aerobic treatment generally results to high biodegradation of TrOC through the action of heterotrophic bacteria and autotrophic ammonia-oxidizing organisms (AOO) in the form of bacteria and archaea [11]. Using 17α-ethinylestradiol as a model pollutant, several research groups have showed that heterotrophs and AOO utilise the enzymes catechol dioxygenase [55] and ammonia monoxygenase [16] for TrOC degradation, respectively. AOO is necessary for the biodegradation of some pharmaceuticals (e.g.…”

“…AOO is necessary for the biodegradation of some pharmaceuticals (e.g. roxithromycin, erythromycin, and iopromide) [13,17,56], although cooperative biodegradation of 17α-ethinylestradiol, trimethoprim, and their metabolites by heterotrophs and AOO has been observed [55].…”

Enrichment and characteristics of ammonia-oxidizing archaea in wastewater treatment process

“…Therefore, compared with AOB, AOA could be easier to accompany with nitrogen and sulfide removal [23][24]. Furthermore, it has been found that the biotransformation of micropollutants were involved with the cometabolism of ammonia-oxidizing microorganisms [25].…”