F. Volkering

Bio: F. Volkering is an academic researcher. The author has contributed to research in topics: Styrene & Styrene oxide. The author has an hindex of 2, co-authored 2 publications receiving 339 citations.

Metabolism of Styrene Oxide and 2-Phenylethanol in the Styrene-Degrading Xanthobacter Strain 124X.

Abstract: Styrene oxide and 2-phenylethanol metabolism in the styrene-degrading Xanthobacter sp. strain 124X was shown to proceed via phenylacetaldehyde and phenylacetic acid. In cell extracts 2-phenylethanol was oxidized by a phenazine methosulfate-dependent enzyme, probably a pyrroloquinoline quinone enzyme. Xanthobacter sp. strain 124X also contains a novel enzymatic activity designated as styrene oxide isomerase. Styrene oxide isomerase catalyzes the isomerization of styrene oxide to phenylacetaldehyde. The enzyme was partially purified and shown to have a very high substrate specificity. Of the epoxides tested, styrene oxide was the only substrate transformed. The initial step in styrene metabolism in Xanthobacter sp. strain 124X is oxygen dependent and probably involves oxidation of the aromatic nucleus.

The biodegradation of aromatic hydrocarbons by bacteria

Abstract: Aromatic compounds of both natural and man-made sources abound in the environment. The degradation of such chemicals is mainly accomplished by microorganisms. This review provides key background information but centres on recent developments in the bacterial degradation of selected man-made aromatic compounds. An aromatic compound can only be considered to be biodegraded if the ring undergoes cleavage, and this is taken as the major criteria for inclusion in this review (although the exact nature of the enzymic ring-cleavage has not been confirmed in all cases discussed).

Review: Biocatalytic transformations of ferulic acid: an abundant aromatic natural product

Abstract: In this review we examine the fascinating array of microbial and enzymatic transformations of ferulic acid. Ferulic acid is an extremely abundant, preformed phenolic aromatic chemical found widely in nature. Ferulic acid is viewed as a commodity scale, renewable chemical feedstock for biocatalytic conversion to other useful aromatic chemicals. Most attention is focused on bioconversions of ferulic acid itself. Topics covered include cinnamoyl side-chain cleavage; nonoxidative decarboxylation; mechanistic details of styrene formation; purification and characterization of ferulic acid decarboxylase; conversion of ferulic acid to vanillin; O-demethylation; and reduction reactions. Biotransformations of vinylguaiacol are discussed, and selected biotransformations of vanillic acid including oxidative and nonoxidative decarboxylation are surveyed. Finally, enzymatic oxidative dimerization and polymerization reactions are reviewed.

Adaptation of Pseudomonas putida S12 to ethanol and toluene at the level of fatty acid composition of membranes.

Abstract: Pseudomonas putida S12 was more tolerant to ethanol when preadapted to supersaturating concentrations of toluene. Cellular reactions at the membrane level to the toxicities of both compounds were different. In growing cells of P. putida S12, sublethal concentrations of toluene resulted in an increase in the degree of saturation of the membrane fatty acids, whereas toxically equivalent concentrations of ethanol led to a decrease in this value. Contrary to this, cells also reacted to both substances with a strong increase of the trans unsaturated fatty acids and a corresponding decrease of the cis unsaturated fatty acids under conditions where growth and other cellular membrane reactions were totally inhibited. While the isomerization of cis to trans unsaturated fatty acids compensates for the fluidizing effect caused by ethanol, a decrease in the degree of saturation is antagonistic with respect to the chemo-physical properties of the membrane. Consequently, the results support the hypothesis that the decrease in the degree of saturation induced by ethanol is not an adaptation mechanism but is caused by an inhibitory effect of the compound on the biosynthesis of saturated fatty acids.

Identification and characterization of the furfural and 5-(hydroxymethyl)furfural degradation pathways of Cupriavidus basilensis HMF14

Abstract: The toxic fermentation inhibitors in lignocellulosic hydrolysates pose significant problems for the production of second-generation biofuels and biochemicals. Among these inhibitors, 5-(hydroxymethyl)furfural (HMF) and furfural are specifically notorious. In this study, we describe the complete molecular identification and characterization of the pathway by which Cupriavidus basilensis HMF14 metabolizes HMF and furfural. The identification of this pathway enabled the construction of an HMF and furfural-metabolizing Pseudomonas putida. The genetic information obtained furthermore enabled us to predict the HMF and furfural degrading capabilities of sequenced bacterial species that had not previously been connected to furanic aldehyde metabolism. These results pave the way for in situ detoxification of lignocellulosic hydrolysates, which is a major step toward improved efficiency of utilization of lignocellulosic feedstock.