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Aryl metabolite biosynthesis was studied in the white rot fungus Bjerkandera adusta cultivated in a liquid medium supplemented with l -phenylalanine. Aromatic compounds were analyzed by gas chromatography-mass spectrometry following addition of labelled precursors ( 14 C- and 13 C-labelled l -phenylalanine), which did not interfere with fungal metabolism. The major aromatic compounds identified were benzyl alcohol, benzaldehyde (bitter almond aroma), and benzoic acid. Hydroxy- and methoxybenzylic compounds (alcohols, aldehydes, and acids) were also found in fungal cultures. Intracellular enzymatic activities (phenylalanine ammonia lyase, aryl-alcohol oxidase, aryl-alcohol dehydrogenase, aryl-aldehyde dehydrogenase, lignin peroxidase) and extracellular enzymatic activities (aryl-alcohol oxidase, lignin peroxidase), as well as aromatic compounds, were detected in B. adusta cultures. Metabolite formation required de novo protein biosynthesis. Our results show that l -phenylalanine was deaminated to trans -cinnamic acid by a phenylalanine ammonia lyase and trans -cinnamic acid was in turn converted to aromatic acids (phenylpyruvic, phenylacetic, mandelic, and benzoylformic acids); benzaldehyde was a metabolic intermediate. These acids were transformed into benzaldehyde, benzyl alcohol, and benzoic acid. Our findings support the hypothesis that all of these compounds are intermediates in the biosynthetic pathway from l -phenylalanine to aryl metabolites. Additionally, trans -cinnamic acid can also be transformed via β-oxidation to benzoic acid. This was confirmed by the presence of acetophenone as a β-oxidation degradation intermediate. To our knowledge, this is the first time that a β-oxidation sequence leading to benzoic acid synthesis has been found in a white rot fungus. A novel metabolic scheme for biosynthesis of aryl metabolites from l -phenylalanine is proposed.

Corynebacterium casei is one of the most prevalent species present on the surfaces of smear-ripened cheeses, where it contributes to the production of the desired organoleptic properties. Here, we report the draft genome sequence of Corynebacterium casei UCMA 3821 to provide insights into its physiology.

Two families of peroxidases—lignin peroxidase (LiP) and manganese-dependent lignin peroxidase (MnP)—are formed by the lignin-degrading white rot basidiomycete Phanerochaete chrysosporium and other white rot fungi. Isoenzymes of these enzyme families carry out reactions important to the biodegradation of lignin. This research investigated the regulation of LiP and MnP production by Mn(II). In liquid culture, LiP titers varied as an inverse function of and MnP titers varied as a direct function of the Mn(II) concentration. The extracellular isoenzyme profiles differed radically at low and high Mn(II) levels, whereas other fermentation parameters, including extracellular protein concentrations, the glucose consumption rate, and the accumulation of cell dry weight, did not change significantly with the Mn(II) concentration. In the absence of Mn(II), extracellular LiP isoenzymes predominated, whereas in the presence of Mn(II), MnP isoenzymes were dominant. The release of 14 CO 2 from 14 C-labeled dehydrogenative polymerizate lignin was likewise affected by Mn(II). The rate of 14 CO 2 release increased at low Mn(II) and decreased at high Mn(II) concentrations. This regulatory effect of Mn(II) occurred with five strains of P. chrysosporium , two other species of Phanerochaete , three species of Phlebia, Lentinula edodes , and Phellinus pini .

The enzymatic degradation of l -methionine and the subsequent formation of volatile sulfur compounds (VSCs) are essential for the development of the typical flavor in cheese. In the yeast Yarrowia lipolytica , the degradation of l -methionine was accompanied by the formation of the transamination product 4-methylthio-2-oxobutyric acid. A branched-chain aminotransferase gene (Yl BCA1 ) of Y. lipolytica was amplified, and the l -methionine-degrading activity and the aminotransferase activity were measured in a genetically modified strain and compared to those of the parental strain. Our work shows that l -methionine degradation via transamination is involved in formation of VSCs in Y. lipolytica .