Ferulic Acid Degradation

Grbic-Galic, D. (1986). Anaerobic production and transformation of aromatic hydrocarbons and substituted phenols by ferulic acid-degrading BESA-inhibited methanogenic consortia. FEMS Microbiology Ecology, 38, 161-9. 

Riittimann-Johnson C, RT Lamar (1996) Polymerization of pentachlorophenol and ferulic acid by fnngal extracellular lignin-degrading enzymes. Appl Environ Microbiol 62 3890-3893. 

Healy and Young (58) observed that the conversion of vanillic and ferulic acids under anaerobic conditions to methane and CO2 was nearly stoichiometric. More than half of the organic carbon could potentially be converted to methane. This could have great importance in studies where the degradation of phenolic compounds are studied by trapping the evolved CO2. Under anaerobic conditions, part of the normal CO2 evolution may be shifted to methane production with a subsequent low reporting of CO2 evolved, and an underestimation of microbial activity in the soil (51). 

The bioconversion of eugenol and ferulic acid to vanillin was first characterised in Pseudomonas fluorescens (Scheme 26.4) [36, 37]. However, an enzyme of the pathway, vanillin NAD+ oxidoreductase, catalysed the removal of vanillin from the medium through the formation of vanillic acid [38]. Deletion of the oxidoreductase was, however, only partially successful, largely because vanillin is also the substrate of coniferyl aldehyde dehydrogenase, an enzyme of the eugenol degradative pathway present in Pseudomonas sp. [39]. 

Reversible sorption of phenolic acids by soils may provide some protection to phenolic acids from microbial degradation. In the absence of microbes, reversible sorption 35 days after addition of 0.5-3 mu mol/g of ferulic acid or p-coumaric acid was 8-14% in Cecil A(p) horizon and 31-38% in Cecil B-t horizon soil materials. The reversibly sorbed/solution ratios (r/s) for ferulic acid or p-coumaric acid ranged from 0.12 to 0.25 in A(p) and 0.65 to 0.85 in B-t horizon soil materials. When microbes were introduced, the r/s ratio for both the A(p) and B-t horizon soil materials increased over time up to 5 and 2, respectively, thereby indicating a more rapid utilization of solution phenolic acids over reversibly sorbed phenolic acids. The increase in r/s ratio and the overall microbial utilization of ferulic acid and/or p-coumaric acid were much more rapid in A(p) than in B-t horizon soil materials. Reversible sorption, however, provided protection of phenolic acids from microbial utilization for only very short periods of time. Differential soil fixation, microbial production of benzoic acids (e.g., vanillic acid and p-hydroxybenzoic acid) from cinnamic acids (e.g., ferulic acid and p-coumaric acid, respectively), and the subsequent differential utilization of cinnamic and benzoic acids by soil microbes indicated that these processes can substantially influence the magnitude and duration of the phytoxicity of individual phenolic acids (Blum, 1998). 

Phenolic aroma compounds can be generated by the thermal radical degradation of phenolic acids such as ferulic acid (52), which is a constituent of many vegetable raw materials [76]. Fig. 3.32 shows the formation scheme for vinylguaiacol (53), vanilline (54) and guaiacol (55) from 52. 

Bonnin, E. et al., Aspergillus niger 1-1472 and Pycnoporus cinnabarinus MUCEL 39533, selected for the biotransformation of ferulic acid to vanillin, are also able to produce cell wall polysaccharide-degrading enzymes and feruloyl esterases, Enzyme Microb. Technol, 28, 70, 2001. 

The production of hydroxyl radicals may be enhanced by addition of benzoyl peroxide [33] or by subjecting the hydrogen peroxide to UV irradiation [34,35], Ferulic acid (Figure 12.1, IV), which is resistant to hydroperoxide anion attack, was degraded by hydrogen peroxide subjected to UV irradiation [36]. 

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