Biodegradation Kinetics of Geometric Isomers of Model Naphthenic Acids in Athabasca River Water

Abstract

The rates ofbiodegradation of six model naphthenic acids (NA$ byheterotrophic bacteria were compared. Specifically, the biodegradation of cis-and trans-geometric isomers of 4-methylcyclohexaneacetic acids (4MACH), 4- hours-1, while the values of K for the corresponding rzi-isomers were 0.7 " 10-3 and 0.6 t 10-'hours-r, respectively. For all the model NAs investigated, the trans tsomers degraded more rapidly than the respective czl isomers. The range of K measured at 10oC and 30"C of the trans-isomers were between 0.6 t 10 3 to 0.8 x 10 3 and2.Ix 10-3 to 7.9 x 10-3 hours-1, respectively, while the corresponding values for the cisisomers were between 0.2 t 10 3 to 0.5 t 10-3 and 1.2 x I}a to 1.8 x 10 3 hours-1, respectively. Intramolecular hydrogen bonding which occurs for only the rzs-isomers, is the proposed rationale for the observed differences in biodegradation kinetics ofthe geometric isomers.

Microbial biodegradation of aromatic alkanoic naphthenic acids is affected by the degree of alkyl side chain branching

“…For non-branched carboxylic acids, the addition of methyl groups hindered b-oxidation (Herman et al, 1993;Alexander, 1999;Smith et al, 2008) and only mixed bacterial populations degraded recalcitrant NAs with methyl substitutions on the cycloalkane rings (Herman et al, 1993;Headley et al, 2002a, b). Differences in NA degradation rates for different geometric isomers have also been observed, whereby intramolecular hydrogen bonding occurring with the cis-isomers makes them less bioavailable and difficult to metabolize (Headley et al, 2002b).…”

Kinetics of the Oxidation of L-Cysteine by trans- and cis-Cobalt(III) and Iron(III) Complexes

“…The concentrations of Cys used [10 −2 -10 −1 mol dm −3 ] were chosen to be 1-2 orders of magnitude larger than that of the MC [10 −4 -10 −2 mol dm −3 ]. The ionic strength of the solutions was kept constant at 0.20 mol dm −3 using NaClO 4 . The temperature of the solution and its pH were both maintained at 25±0.1 • C and 7.0 ± 0.1, respectively.…”

“…Toma et al [3] reviewed linkage isomerization reactions from the aspect of kinetics and mechanisms involved, some focusing on selected cases of direct formation, as well as on electrochemical, photochemical, thermal and pH-induced generation of linkage isomers. The biodegradation kinetics of geometric isomers of model naphthenic acid in water has been studied by Peru et al [4]. The rates of biodegradation of six model naphthanic acids by heterotrophic bacteria were compared.…”

The impact of various ozone pretreatment doses on the performance of endogenous microbial communities for the remediation of oil sands process-affected water

“…Other studies have reported that the molecular weight (Scott et al, 2005;Biryukova et al, 2007;Whitby, 2010) and chemical structure (Headley et al, 2002;Smith et al, 2008;Han et al, 2008) of NAs can influence their biodegradation. For instance, determinants of recalcitrant NAs can include the following: (i) a higher degree of alkyl-substituted aliphatic chains (Smith et al, 2008;Han et al, 2008), (ii) tertiary substitution at positions other than the b-position to the carboxylic acid of the main carbon chain, (iii) methyl substitution on the cycloalkane rings (Herman et al, 1993;Smith et al, 2008), (iv) increased cyclicity (Han et al, 2008), (v) evenness of the carbon side chain, and (vi) cis-isomerism in alicyclic acids (Headley et al, 2002;Holowenko et al, 2002). Ozonation could change the molecular weight and chemical structure of NAs by decomposing long chains and by breaking highly-branched and cyclic carboxylic fractions, thereby improving their biodegradation.…”