A multipathogen selective enrichment broth (SVV) for simultaneous growth of Salmonella, Vibrio parahaemolyticus, and Vibrio cholerae / 生物工程学报

We formulated a selective enrichment broth (SVV) for simultaneous growth of Salmonella, Vibrio parahaemolyticus, and Vibrio cholerae by single factor experiment and response surface method. We evaluated the enrichment effect of SVV by conventional culture method and real-time PCR assay. We obtained the SVV broth by supplementting the Buffered Peptone Water (BPW) with bile salt no. 3, potassium tellurite, and sodium citrate as inhibitors, and glucose, mannitol, snhydrous sodium sulfite and sodium pyruvate as accelerants. We also modified the concentration of sodium chloride in BPW. When mixed at equal or varied proportions, the target pathogens had a great accumulation (10(5)-10(8) CFU/mL) after incubated in SVV for 18 h at 37 degrees C with shaking. It can also effectively inhibit the competitive microflora. We detected 10 artificial simulated samples and 608 real samples using SVV with real-time PCR. After enriched in SVV for 18 h, the quantity of the bacteria in samples were above the detection limit. The SVV with PCR assay showed higher tested positive (4.06%) compared to that of the conventional detection method (3.78%) and there was no false report. In summary, SVV is a promising new multiplex selective enrichment broth that can be used in detection of seafood.

Global expression profiling of Saccharomyces cerevisiae: metabolic remodeling in post-log phase / 生物工程学报

For the purpose of revealing the mechanism of the reduction of yeasts ethanol production rate after entrance of post-log phase, we used microarray to study expression profiles of the yeast Saccharomyces cerevisiae during the transition from mid-log growth phase to post-log growth. The results demonstrate that the global pattern of gene expression is very stable during the mid-log phase. However, a dramatic metabolic remodeling was found when the yeast entries post-log phase, during which many of amino acid synthesis and metabolism related genes are up-regulated, moreover, ion transport, energy generation and storage related genes are also up regulated during this phase, while a large number of genes involved in transposition and DNA recombination are repressed. Central metabolic pathways also engage in metabolic remodeling, within which the genes involved in succinate and a-ketoglutarate synthesis pathways are up regulated, accordance with those of amino acid synthesis and metabolism. These results demonstrate that the increasing demand for amino acids in post-log phase lead to a metabolic transition into TCA cycle and glyoxylate cycle, which subsequently reduce the ethanol production rate. This suggests a global insight into the process of yeast ethanol fermentation.