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Abstract <p>Benzyl alcohol (BA) and two BA esters were examined for their ability to support growth of <i>Burkholderia vietnamiensis</i> G4 and expression of toluene-2-monooxygenase (T2MO) activity. Resting cell assays and an activity-based labeling (ABL) approach were used to quantify T2MO activity and levels of T2MO hydroxylase subunit in cells grown either on substrates already known to support T2MO expression (toluene, phenol); novel aromatic substrates (BA, benzyl acetate (BAc); benzyl butyrate (BBu)); and non-aromatics (lactate, acetate, and butyrate). Specific rates of TCE oxidation and levels of activity-based fluorescent labeling of T2MO hydroxylase α-subunits in cells grown on BA or BA esters were comparable to or greater than those of cells grown on toluene or phenol. In contrast, levels of activity and protein labeling of cells grown on acetate or butyrate were like those of lactate-grown cells. Cells grown on BA also degraded 1,2-<i>cis</i>-dichloroethene (<i>cis</i>-DCE), 1,1-dichloroethene (1,1-DCE), and vinyl chloride (VC). While toluene-grown cells generally exhibited higher specific rates of chloroethene transformation, BA-grown cells had consistently higher transformation capacities for these compounds. Stable accumulation of BA in batch cultures grown on BBu in the presence of propyne and the inhibitory effects of BA on TCE transformation both suggest BA is a T2MO substrate. Substrate-specific O<sub>2</sub> uptake studies also suggest 2-hydroxybenzyl alcohol is a likely product of T2MO-dependent BA oxidation. Our results suggest that BA and benzyl esters could be useful for promoting cometabolic transformations, because unlike toluene or phenol, these are “generally regarded as safe” (GRAS) compounds with little or no human toxicity.</p> Key points <p>• <i>Burkholderia vietnamiensis G4 cometabolizes TCE when grown on benzyl alcohol (BA).</i></p> <p>•<i> Activity-based labeling showed BA and BA producing esters support T2MO expression.</i></p> <p>• <i>BA and BA producing esters are safe compounds to promote aerobic TCE transformation</i>.</p>

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Toluene-2-monooxygenase expression and trichloroethene oxidizing activity of Burkholderia vietnamiensis G4 grown on benzyl alcohol and benzyl esters

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  • 发表日期：

    2025年12月19日

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  • Alyssa M. Saito,
  • Alejandra P. Oyarzún,
  • Michael R. Hyman,
  • Lewis Semprini

摘要

Abstract

Benzyl alcohol (BA) and two BA esters were examined for their ability to support growth of Burkholderia vietnamiensis G4 and expression of toluene-2-monooxygenase (T2MO) activity. Resting cell assays and an activity-based labeling (ABL) approach were used to quantify T2MO activity and levels of T2MO hydroxylase subunit in cells grown either on substrates already known to support T2MO expression (toluene, phenol); novel aromatic substrates (BA, benzyl acetate (BAc); benzyl butyrate (BBu)); and non-aromatics (lactate, acetate, and butyrate). Specific rates of TCE oxidation and levels of activity-based fluorescent labeling of T2MO hydroxylase α-subunits in cells grown on BA or BA esters were comparable to or greater than those of cells grown on toluene or phenol. In contrast, levels of activity and protein labeling of cells grown on acetate or butyrate were like those of lactate-grown cells. Cells grown on BA also degraded 1,2-cis-dichloroethene (cis-DCE), 1,1-dichloroethene (1,1-DCE), and vinyl chloride (VC). While toluene-grown cells generally exhibited higher specific rates of chloroethene transformation, BA-grown cells had consistently higher transformation capacities for these compounds. Stable accumulation of BA in batch cultures grown on BBu in the presence of propyne and the inhibitory effects of BA on TCE transformation both suggest BA is a T2MO substrate. Substrate-specific O2 uptake studies also suggest 2-hydroxybenzyl alcohol is a likely product of T2MO-dependent BA oxidation. Our results suggest that BA and benzyl esters could be useful for promoting cometabolic transformations, because unlike toluene or phenol, these are “generally regarded as safe” (GRAS) compounds with little or no human toxicity.

Key points

• Burkholderia vietnamiensis G4 cometabolizes TCE when grown on benzyl alcohol (BA).

• Activity-based labeling showed BA and BA producing esters support T2MO expression.

• BA and BA producing esters are safe compounds to promote aerobic TCE transformation.