The tobacco-specific nitrosamines (TSNAs) are one of the most important groups of carcinoigens in tobacco leaf, knowing the difference of TSNAs contents in tobacco genotypes should be beneficial for breeding low TSNAs cultivars which could decrease the harmfulness to human health in tobacco products. For this purpose, 8 genotypes (include burley, sun-cured and flue-cured tobacco) were selected as materials, the TSNAs contents of uncured and cured leaves were assessed with LC-MS/MS. The results showed that TSNAs contents were significantly increased after curing in all genotypes. The mean TSNAs contents of leaves before and after curing in burley were the highest among three types of tobacco, and the contents in sun-cured tobacco were the lowest. Coefficient of variation (CV) of TSNAs among genotypes in burley was higher than that in flue-cured and sun-cured tobacco, and the CV in sun-cured tobacco was the lowest. The positive correlation was observed in NNN, NAT and total TSNAs contents between uncured and cured leaves in three types of tobacco. Therefore, the TSNAs contents in uncured leaves could be considered as evaluation index to screen tobacco cultivars with the low TSNAs contents.

Microencapsulation can improve the thermal stability of a fragrance, and composite wall materials are one way to further improve the thermal stability of microcapsules. This paper presents a facile approach for cotton fabric coatings by using cellulose/silica hybrid microcapsules. Lavender fragrance oil-loaded cellulose/silica hybrid microcapsules were one-step synthesized via emulsion solvent diffusion. The prepared microcapsules were found to be spherical in shape with a particle size distribution between 500 to 1000 nm. Due to the slow releasing of lavender fragrance oil in the capsules, the fragrance loss rate of (3-aminopropyl)triethoxysilane (APTES)-, triethoxy(3-glycidyloxypropyl)silane (GPTES)-, and (3-aercaptopropyl)trie-thoxysilane (MPTES)- modified cellulose/silica hybrid microcapsules are 25.2%, 35.1%, and 16.7% after six hours at 120 °C. E-nose and gas chromatography–mass spectrometry (GCMS) studies found that the fragranced cotton fabrics had good retention of characteristic aromas. It provides the basis for the application of the heating treatment of cotton fabrics in sterilization, bleaching, printing, and other processes.

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BackgroundTryptophol (TOL) is a metabolic derivative of tryptophan (Trp) and shows pleiotropic effects in humans, plants and microbes. The mechanisms of TOL biosynthesis were first explored several decades ago. Nonetheless, a systematic interpretation of TOL over-accumulation is still lacking.ResultsBased on TOL yield, a suitable transformation medium (TM1) was used to culture Saccharomyces cerevisiae strain KMLY1-2. The dynamics of TOL production, cell growth, and gene transcription revealed that TOL production was dependent on cell density and the expression of key genes. Additionally, the effects of Trp and phenylalanine (Phe) on TOL production were tested, and the results showed that Trp can significantly facilitate TOL accumulation, but output plateaued (231.02−266.31 mg/L) at Trp concentrations ≥0.6 g/L. In contrast, Phe reduced the stimulatory effect of Trp, which strongly depended on the Phe concentration. To elucidate the molecular basis and regulatory mechanism of TOL overproduction, an integrated analysis of metabolomics, genomics, and transcriptomics was performed. The results revealed that 1) both the Ehrlich pathway and tryptamine-dependent pathway were involved in S. cerevisiae TOL biosynthesis; 2) Trp increased TOL production by enhancing the Ehrlich pathway, in which the steps of transamination (including aminotransferase genes aro9, aat1, bat2 and his5) and decarboxylation (including decarboxylase genes aro10 and pdc5) played important roles. Of course, this process was assisted by amino acid permease genes agp1 and tat2, dihydrolipoyl dehydrogenase gene lpd1, and transcriptional activator gene aro80, etc.; 3) Phe restricted TOL biosynthesis by repressing the transcript levels of genes such as aat1, his5, aro10, pdc5 and aro80, thus interfering with the transamination and decarboxylation reactions; and 4) under sufficient Trp conditions, the de novo Trp biosynthetic pathway and central carbon metabolism (glycolysis, pentose phosphate pathway, and citrate cycle) of S. cerevisiae were weakened, while the content of some amino acids increased, which may be related to the promotion of yeast cell growth by Trp.ConclusionsIn this study, TOL production of S. cerevisiae was significantly improved, and our integrated multi-omics analyses have provided insights into the understanding of TOL over-accumulation, which will be useful for future production of TOL using metabolic engineering strategies.