The degradation of sinapic acid, a monomer of hardwood lignins, by the yeast Rhodotorula glutinis was studied. Syringic acid, 3-0-methyl gallic acid, gallic acid and 2,6-dimethoxy-1,4benzoquinone were identified as degradation products. Glucose was shown to be required for the demethylation of the methoxy groups on the ring. Unlike in the bacterium Pseudomonas putida, ring cleavage seemed to occur via gallic acid and not via methyl gallic acid. Cell-free oxidative decarboxylase (hydroxylase) activity was detected ; this enzyme might be ultimately responsible for the formation of dimethoxyquinone. I N T R O D U C T I O N One reason for studying the microbial metabolism of aromatic compounds is to understand the reactions involved in the degradation of lignin. As hardwood lignins contain syringic-type structural elements (Adler, 1977; Nimz, 1974), syringic acid and sinapic acid can serve as monomeric models for these degradation studies. Degradation of syringic acid both by bacteria (Sparnins & Dagley, 1975) and fungi (Eriksson et al., 1984; Iyayi & Dart, 1982; Haider & Trojanowski, 1975) has been reported. In the course of degradation studies of sinapyl alcohol, the wood-rotting fungus Schizophyllum commune was shown to be able to degrade sinapic acid (Iyayi &Dart, 1982). There is, however, no detailed report in the literature on the metabolism of sinapic acid by a yeast. Yeasts of the genus Rhodotorula have been shown to be able to degrade chlorophenols (Walker, 1973) as well as vanillic and ferulic acid which represent the guaiacyl (soft-wood) lignins (Cain et al., 1968). The isolation of Rhodotorula grinbergsii from decaying wood (Ramirez & Gonzalez, 1984) indicates that this yeast might be involved in the process of wood decay. We now report on the degradation of sinapic acid by the yeast Rhodotorula glutinis.
SUMMARYBy far the most abundant hydrocarbon in unpolluted air is methane (mixing ratio ca. 1.6 ppm). The mixing ratios of other hydrocarbons are typically in the low parts per 10 9 (ppb) and parts per 10 12 (ppt) ranges. Although methane is several orders of magnitude more abundant in clean air, it is conceivable that other hydrocarbons are still of considerable importance to clean air photochemistry, because their reaction with hydroxyl radicals proceeds much faster than that of methane.Owing to this high reactivity of many of the light non-methane hydrocarbons (NMHC), mixing ratios of NMHC as low as a few ppb or several ppt can have a considerable influence on the photochemistry of unpolluted air. For this reason a gas chromatographic method has been developed that permits the determination of several C 2 -C S hydrocarbons with detection limits of a few ppt from grab samples of 0.5-2 dm 3 (STP).The samples are collected in evacuated 2-1 stainless-steel containers with metal bellows-sealed stainless-steel valves. These sample collection and storage cans are specially pre-treated and cleaned to avoid changes in sample composition during transport of the samples to the laboratory. In the laboratory the samples are analysed by enrichment of the hydrocarbons on a packed pre-column at sub-ambient temperatures (ca. -35°C) and subsequent separation on a 7 m x O.8mm LO. packed column (Spherosil XOB 075). A flame-ionization detector is used. This method allowed survey measurements on a global scale of C 2 -C S hydrocarbons. which gave an estimate of the contributions of light hydrocarbons to atmospheric photochemical reactions.
INTRODUCTIONWith a mixing ratio of about 1.6 ppm, methane is by far the most abundant hydrocarbon in unpolluted air. The mixing ratios of other hydrocarbons are several orders of magnitude lower at a few parts per 10 9 (ppb) or fractions of I ppb 1 • However. this does not necessarily mean that the non-methane hydrocarbons (NMHC) are of no importance to the chemistry of the unpolluted atmosphere. The importance of an atmospheric trace component to atmospheric photochemistry is determined not only by its abundance but also by its participation in photochemical reaction chains and cycles. According to current understanding of atmospheric chem-
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