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1. (Article ID: 8582)
 
Liu H, Gong F, Wei F, Lai F, Zhang X, Wu H
Artificial simulated gastrointestinal digestion of four carbohydrates containing beta-D-1→4 linkages and new GC-TQ/MS-MS method for characterising released monosaccharides
International Journal of Food Science and Technology 53(8) (2018) 1992-2005
 

Four types of carbohydrates, including Dendrobium officinale polysaccharide, Dendrobium aphyllum polysaccharide and β-glucans from yeast and barley, were examined, and their structures were found to mainly contain 1,4-linked-β-D-Glcp. Artificially simulated gastrointestinal digestion was conducted to characterise the changes of molecular weight, reducing sugars and released free monosaccharides by high-performance liquid chromatography, kits and the newly developed gas chromatography (GC)-mass spectrometry (MS)/MS analysis, which indicated that high molecular weight and complex spatial structures contributed to delayed monosaccharide release following exposure to digestive solution. The spatial structures of carbohydrates were changed during gastric digestion, but their primary structures were destroyed during intestinal digestion. Additionally, for the developed 7890A/7000 GC-TQ/MS-MS, the new analytical method was successfully used to analyse very low concentrations of monosaccharides in the simulated gastrointestinal digestive system.

polysaccharide, β-glucan, In vitro digestion, D-β-1-4 linkages, GC-TQ/MS-MS, released monosaccharides

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2. (Article ID: 8895)
 
Silva R, Aguiar TQ, Oliveira C, Domingues L
Physiological characterization of a pyrimidine auxotroph exposes link between uracil phosphoribosyltransferase regulation and riboflavin production in Ashbya gossypii
New Biotechnology 50 (2019) 1-8
 

The blockage of the de novo pyrimidine biosynthetic pathway at the orotidine-5'-phosphate decarboxylase level was previously demonstrated to affect riboflavin production in the industrial producer fungus Ashbya gossypii. However, the molecular basis for the unusual sensitivity to uracil displayed by the pyrimidine auxotroph A. gossypii Agura3 was unknown. Here, uridine was shown to be the only intermediate of the pyrimidine salvage pathway able to fully restore this mutant's growth. Conversely, uracil, which is routinely used to rescue pyrimidine auxotrophs, had a dose-dependent growth-inhibitory effect. Uracil phosphoribosyltransferase (UPRT) is the pyrimidine salvage pathway enzyme responsible for converting uracil to uridine monophosphate in the presence of phosphoribosyl pyrophosphate (PRPP). Characterization of the A. gossypii UPRT, as produced and purified from Escherichia coli, revealed that uracil concentrations above 1 mM negatively affected its activity, thus explaining the hypersensitivity of the Agura3 mutant to uracil. Accordingly, overexpression of the AgUPRT encoding-gene in A. gossypii Agura3 led to similar growth on rich medium containing 5 mM uracil or uridine. Decreased UPRT activity ultimately favors the preservation of PRPP, which otherwise may be directed to other pathways. In A. gossypii, increased PRPP availability promotes overproduction of riboflavin. Thus, this UPRT modulation mechanism reveals a putative means of saving precursors essential for riboflavin overproduction by this fungus. A similar uracil-mediated regulation mechanism of the UPRT activity is reported only in two protozoan parasites, whose survival depends on the availability of PRPP. Physiological evidence here discussed indicate that it may be extended to other distantly related flavinogenic fungi.

Ashbya gossypii, auxotrophy, phosphoribosyltransferase, pyrimidine metabolism, riboflavin production, uracil, uracil/uridine

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3. (Article ID: 8896)
 
Song Y-P, Miao F-P, Liu X-H, Yin X-L, Ji N-Y
Seven chromanoid norbisabolane derivatives from the marine-algaendophytic fungus Trichoderma asperellum A-YMD-9-2
Fitoterapia 135 (2019) 107–113
 

An examination of the endophytic fungus Trichoderma asperellum A-YMD-9-2 obtained from the marine red alga Gracilaria verrucosa led to the isolation of seven new chromanoid norbisabolane derivatives, trichobisabolins I–L (1–4) and trichaspsides C–E (5–7). Their structures and relative configurations were established on the basis of spectroscopic techniques, mainly including 1D/2D NMR and MS, and the absolute configuration of 1 was assigned by X-ray crystallographic analysis using Cu Kα radiation. All of these isolates feature a 1,9-epoxy ring system, and 5–7 represent the second occurrence of norbisabolane aminoglycosides. Compounds 1–7 exhibited potent inhibition of several marine phytoplankton species.

Trichoderma, sesquiterpene, terpene, bisabolane, norbisabolane

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