ABSTRACT
Nitrogen is an essential nutrient for yeast cells on ethanol fermentation. In order to reveal the promoting mechanisms of organic nitrogen sources on the ethanol fermentation by yeast, Saccharomyces cerevisiae, laser tweezers Raman spectroscopy and single-cell analysis techniques were used to monitored the kinetic of intracellular bio-macromolecules of individual cells during fermentation with urea, yeast extract, ammonium nitrate or ammonium sulfate as the sole nitrogen source. Major results from this work were as follows. (1) Organic nitrogen sources had a promoting effect on the ethanol fermentation, the fermentation with urea and yeast extract reached the maximum concentration of ethanol in 14-18 h. ( 2 ) There were no apparent lag phases for the RNA synthesis of yeast cells cultured with urea and yeast extract. The averaged Raman intensity of yeast cells at peak of 782 cm-1 in the early stage of fermentation was stronger than that of cultured with ammonium nitrate and ammonium sulfate. The maximum was about 1. 9-2. 1 times of the initial intensity for urea or yeast extract, but 1. 2-1. 4 times for ammonium nitrate and ammonium sulfate. (3) The secondary structure of proteins of partial cells cultured with yeast extract was dominated byβ-sheet, while cells cultured with other nitrogen sources were dominated by α-helix absolutely. These results bring us the conclusion that the improving effect of organic nitrogen sources such as urea and yeast extract on ethanol fermentation by Saccharomyces cerevisiae may be due to that the organic nitrogen sources can shorten the lag phase of yeast cells, promote the RNA synthesis, and promote the transcription and expression of related genes.
ABSTRACT
Objective To investigate the effects of curcumin on mRNA expression of cytokines related to Toll-like receptor (TLR) 4 signaling in THP-1 cells.Methods After pretreatment with different concentrations (50,25,12.5 mg/L) of curcumin or dexamethasone for 12 hours,THP-1 cells were stimulated by lipopolysaccharide (LPS.1 mg/L) for 4 hours followed by the collection of cells.Then total RNA was isolated from these cells and subjected to reverse transcription-polymerase chain reaction (RT-PCR) for the detection of mRNA expression of tumor necrosis factor receptor-associated factor 6 (TRAF6),interleukin-1 receptorassociated kinase (IRAK1) and nuclear factor (NF)-κB.THP-1 cells without pretreatment or stimulation served as negative control,and those only stimulated with LPS served as LPS group.Results After stimulation with LPS (1 mg/L) for 4 hours,the mRNA expressions of TRAF6,IRAK1 and NF-κB were significantly upregulated in THP-1 cells compared with negative control cells (f=38.69,39.13,23.99,all P<0.01).Curcumin of 50 mg/L and 25 mg/L significantly inhibited the mRNA expressions of TRAF6.IRAK 1 and NF-κB upregulated by LPS with an inhibition rate of more than 50% (all P<0.0 1).Conclusions Certain concentrations of curcumin can inhibit the mRNA expressions of TRAF6.IRAK1 and NF-κB.which demonstrates the regulatory effect of curcumin on the mRNA expressions of TLR4 signaling pathway-associated cytokines.