Methanogenic Decomposition of Ferulic Acid, a Model Lignin Derivative

Abstract

Ferulic acid, a model lignin derivative, was observed to be biodegradable to methane and carbon dioxide under strict anaerobic conditions. This conversion appears to be carried out by a consortium of bacteria similar to that previously described for the methanogenic degradation of benzoic acid. A temporary buildup of acetate in these cultures indicates that it is a likely intermediate and precursor for methane formation. An analog of coenzyme M, 2-bromoethanesulfonic acid (BESA), inhibited gas production and enhanced the buildup of propionate, butyrate, isobutyrate, and isovalerate. Phenylacetate, cinnamate, 3-phenylpropionate, benzoate, cyclohexane carboxylate, adipate, and pimelate were also detected in BESA-inhibited cultures. A pathway is proposed which includes these various acids as possible intermediates in the methanogenic degradation of ferulic acid. This model overlaps previously described benzoic acid degradation pathways, suggesting that this type of anaerobic degradation may be common for aromatic compounds.

Anaerobic production and transformation of aromatic hydrocarbons and substituted phenols by ferulic acid-degrading BESA-inhibited methanogenic consortia

“…6 mth before the onset of these experiments, 1 mM of BESA was added to inhibit methanogenesis. After 5 mth, the cultures were fed ferulic acid once more, and substrate concentration in inhibited cultures was monitored with UV-spectrophotometry while gas production was measured with a glass syringe and analyzed with a gas partitioner [2]. The initial substrate disappeared completely in one month, but only an average of 4.5 mmol gas (CO 2 exclusively) was produced from 30 mmol substrate carbon.…”

“…Concentration (mM carbon) " with high pressure liquid chromatography (HPLC) in similar cultures [2,5]. In later stages of incubation, complex aromatic acids are converted mostly to simpler intermediates (phenylpropionic, phenylacetic, benzoic acids) and substituted phenols which temporarily accumulate and then slowly disappear, or remain as dead-end metabolites (see Figs.…”

“…It has been shown that lignin-derived monoaromatic alcohols and acids can be completely degraded under methanogenic conditions [1][2][3][4][5]. The populations capable of such transformations are complex communities consisting of strictly anaerobic [6] and facultatively anaerobic fermentative bacteria [7,8], methanogens [5], and possibly also hydrogen-producing acetogens as an intermediary link between the two groups.…”

Anaerobic Metabolism of Aromatic Compounds

“…a-Oxidation of carboxymethyl groups. Phenylacetate and 4-hydroxyphenylacetate are catabolites in the degradation of even-numbered w-phenyl fatty acids (Elder et al, 1992a, b), phenylalanine (Schneider, S., Mohamed, M. and Fuchs, G., unpublished), tyrosine (Barker, 1981) and lignin monomers (Healy et al, 1980;Grbic-Galic, 1985). Both can be degraded under anaerobic conditions by a number of denitrifying and sulfate-reducing bacteria (Widdel and Pfennig, 1984;Sembiring and Winter, 1989;Seyfried et al, 1991 ;Dangel et al, 1991).…”

Methanogenic degradation of hydroquinone and catechol via reductive dehydroxylation to phenol

“…These substrates were therefore often considered recalcitrant in the absence of molecular oxygen [2], and catechol especially was found to be quite stable under anaerobic conditions [3,4]. Nonetheless, complete methanogenic degradation of phenolic and other aromatic compounds such as lignin monomers has been reported [5][6][7]. Methanogenic degradation of benzoate depends on a syntrophic co-operation of fermentative and hydrogen-oxidizing methanogenic bacteria [8,9], whereas trihydroxybenzoates and trihydroxybenzenes were fermented to acetate in pure culture [10].…”